# HG changeset patch
# User Tyler Trahan <tyler@tylertrahan.com>
# Date 2023-08-16 13:43:31
# Node ID 803962be032894317c2070d4e67b560e29284463
# Parent  ddbd33508a8a76a47468c5b97826138eee0f4a15

Codechange: Move date consts and functions to CalendarTime and TimerGameCalendar classes

diff --git a/src/aircraft_cmd.cpp b/src/aircraft_cmd.cpp
--- a/src/aircraft_cmd.cpp
+++ b/src/aircraft_cmd.cpp
@@ -453,7 +453,7 @@ void Aircraft::OnNewDay()
 
 	if (this->running_ticks == 0) return;
 
-	CommandCost cost(EXPENSES_AIRCRAFT_RUN, this->GetRunningCost() * this->running_ticks / (DAYS_IN_YEAR * Ticks::DAY_TICKS));
+	CommandCost cost(EXPENSES_AIRCRAFT_RUN, this->GetRunningCost() * this->running_ticks / (CalendarTime::DAYS_IN_YEAR * Ticks::DAY_TICKS));
 
 	this->profit_this_year -= cost.GetCost();
 	this->running_ticks = 0;
diff --git a/src/build_vehicle_gui.cpp b/src/build_vehicle_gui.cpp
--- a/src/build_vehicle_gui.cpp
+++ b/src/build_vehicle_gui.cpp
@@ -967,7 +967,7 @@ int DrawVehiclePurchaseInfo(int left, in
 	if (e->type != VEH_TRAIN || e->u.rail.railveh_type != RAILVEH_WAGON) {
 		/* Design date - Life length */
 		SetDParam(0, ymd.year);
-		SetDParam(1, DateToYear(e->GetLifeLengthInDays()));
+		SetDParam(1, TimerGameCalendar::DateToYear(e->GetLifeLengthInDays()));
 		DrawString(left, right, y, STR_PURCHASE_INFO_DESIGNED_LIFE);
 		y += FONT_HEIGHT_NORMAL;
 
diff --git a/src/cheat_gui.cpp b/src/cheat_gui.cpp
--- a/src/cheat_gui.cpp
+++ b/src/cheat_gui.cpp
@@ -104,7 +104,7 @@ extern void EnginesMonthlyLoop();
 static int32_t ClickChangeDateCheat(int32_t new_value, int32_t change_direction)
 {
 	/* Don't allow changing to an invalid year, or the current year. */
-	auto new_year = Clamp(TimerGameCalendar::Year(new_value), MIN_YEAR, MAX_YEAR);
+	auto new_year = Clamp(TimerGameCalendar::Year(new_value), CalendarTime::MIN_YEAR, CalendarTime::MAX_YEAR);
 	if (new_year == TimerGameCalendar::year) return static_cast<int32_t>(TimerGameCalendar::year);
 
 	TimerGameCalendar::YearMonthDay ymd;
@@ -320,7 +320,7 @@ struct CheatWindow : Window {
 					switch (ce->str) {
 						/* Display date for change date cheat */
 						case STR_CHEAT_CHANGE_DATE:
-							SetDParam(0, TimerGameCalendar::ConvertYMDToDate(MAX_YEAR, 11, 31));
+							SetDParam(0, TimerGameCalendar::ConvertYMDToDate(CalendarTime::MAX_YEAR, 11, 31));
 							width = std::max(width, GetStringBoundingBox(ce->str).width);
 							break;
 
diff --git a/src/company_gui.cpp b/src/company_gui.cpp
--- a/src/company_gui.cpp
+++ b/src/company_gui.cpp
@@ -1861,7 +1861,7 @@ struct CompanyInfrastructureWindow : Win
 		}
 
 		/* Get the date introduced railtypes as well. */
-		this->railtypes = AddDateIntroducedRailTypes(this->railtypes, MAX_DATE);
+		this->railtypes = AddDateIntroducedRailTypes(this->railtypes, CalendarTime::MAX_DATE);
 
 		/* Find the used roadtypes. */
 		for (const Engine *e : Engine::IterateType(VEH_ROAD)) {
@@ -1871,7 +1871,7 @@ struct CompanyInfrastructureWindow : Win
 		}
 
 		/* Get the date introduced roadtypes as well. */
-		this->roadtypes = AddDateIntroducedRoadTypes(this->roadtypes, MAX_DATE);
+		this->roadtypes = AddDateIntroducedRoadTypes(this->roadtypes, CalendarTime::MAX_DATE);
 		this->roadtypes &= ~_roadtypes_hidden_mask;
 	}
 
diff --git a/src/date_gui.cpp b/src/date_gui.cpp
--- a/src/date_gui.cpp
+++ b/src/date_gui.cpp
@@ -44,8 +44,8 @@ struct SetDateWindow : Window {
 			Window(desc),
 			callback(callback),
 			callback_data(callback_data),
-			min_year(std::max(MIN_YEAR, min_year)),
-			max_year(std::min(MAX_YEAR, max_year))
+			min_year(std::max(CalendarTime::MIN_YEAR, min_year)),
+			max_year(std::min(CalendarTime::MAX_YEAR, max_year))
 	{
 		assert(this->min_year <= this->max_year);
 		this->parent = parent;
diff --git a/src/date_type.h b/src/date_type.h
--- a/src/date_type.h
+++ b/src/date_type.h
@@ -12,72 +12,5 @@
 
 #include "timer/timer_game_calendar.h"
 
-static const int DAYS_IN_YEAR      = 365; ///< days per year
-static const int DAYS_IN_LEAP_YEAR = 366; ///< sometimes, you need one day more...
-static const int MONTHS_IN_YEAR    =  12; ///< months per year
-
-static const int SECONDS_PER_DAY   = 2;   ///< approximate seconds per day, not for precise calculations
-
-/*
- * ORIGINAL_BASE_YEAR, ORIGINAL_MAX_YEAR and DAYS_TILL_ORIGINAL_BASE_YEAR are
- * primarily used for loading newgrf and savegame data and returning some
- * newgrf (callback) functions that were in the original (TTD) inherited
- * format, where 'TimerGameCalendar::date == 0' meant that it was 1920-01-01.
- */
-
-/** The minimum starting year/base year of the original TTD */
-static constexpr TimerGameCalendar::Year ORIGINAL_BASE_YEAR = 1920;
-/** The original ending year */
-static constexpr TimerGameCalendar::Year ORIGINAL_END_YEAR = 2051;
-/** The maximum year of the original TTD */
-static constexpr TimerGameCalendar::Year ORIGINAL_MAX_YEAR = 2090;
-
-/**
- * Calculate the date of the first day of a given year.
- * @param year the year to get the first day of.
- * @return the date.
- */
-static constexpr TimerGameCalendar::Date DateAtStartOfYear(TimerGameCalendar::Year year)
-{
-	int32_t year_as_int = static_cast<int32_t>(year);
-	uint number_of_leap_years = (year == 0) ? 0 : ((year_as_int - 1) / 4 - (year_as_int - 1) / 100 + (year_as_int - 1) / 400 + 1);
-
-	return (DAYS_IN_YEAR * year_as_int) + number_of_leap_years;
-}
-
-/**
- * Calculate the year of a given date.
- * @param date The date to consider.
- * @return the year.
- */
-static inline TimerGameCalendar::Year DateToYear(TimerGameCalendar::Date date)
-{
-	return static_cast<int32_t>(date) / DAYS_IN_LEAP_YEAR;
-}
-
-/**
- * The date of the first day of the original base year.
- */
-static constexpr TimerGameCalendar::Date DAYS_TILL_ORIGINAL_BASE_YEAR = DateAtStartOfYear(ORIGINAL_BASE_YEAR);
-
-/** The absolute minimum & maximum years in OTTD */
-static constexpr TimerGameCalendar::Year MIN_YEAR = 0;
-
-/** The default starting year */
-static constexpr TimerGameCalendar::Year DEF_START_YEAR = 1950;
-/** The default scoring end year */
-static constexpr TimerGameCalendar::Year DEF_END_YEAR = ORIGINAL_END_YEAR - 1;
-
-/**
- * MAX_YEAR, nicely rounded value of the number of years that can
- * be encoded in a single 32 bits date, about 2^31 / 366 years.
- */
-static constexpr TimerGameCalendar::Year MAX_YEAR = 5000000;
-
-/** The date of the last day of the max year. */
-static constexpr TimerGameCalendar::Date MAX_DATE = DateAtStartOfYear(MAX_YEAR + 1) - 1;
-
-static constexpr TimerGameCalendar::Year INVALID_YEAR = -1; ///< Representation of an invalid year
-static constexpr TimerGameCalendar::Date INVALID_DATE = -1; ///< Representation of an invalid date
 
 #endif /* DATE_TYPE_H */
diff --git a/src/depot_gui.cpp b/src/depot_gui.cpp
--- a/src/depot_gui.cpp
+++ b/src/depot_gui.cpp
@@ -360,7 +360,7 @@ struct DepotWindow : Window {
 			DrawSpriteIgnorePadding((v->vehstatus & VS_STOPPED) ? SPR_FLAG_VEH_STOPPED : SPR_FLAG_VEH_RUNNING, PAL_NONE, flag, false, SA_CENTER);
 
 			SetDParam(0, v->unitnumber);
-			DrawString(text, STR_JUST_COMMA, (v->max_age - DAYS_IN_LEAP_YEAR) >= v->age ? TC_BLACK : TC_RED);
+			DrawString(text, STR_JUST_COMMA, (v->max_age - CalendarTime::DAYS_IN_LEAP_YEAR) >= v->age ? TC_BLACK : TC_RED);
 		}
 	}
 
diff --git a/src/economy.cpp b/src/economy.cpp
--- a/src/economy.cpp
+++ b/src/economy.cpp
@@ -735,7 +735,7 @@ bool AddInflation(bool check_year)
 	 * inflation doesn't add anything after that either; it even makes playing
 	 * it impossible due to the diverging cost and income rates.
 	 */
-	if (check_year && (TimerGameCalendar::year < ORIGINAL_BASE_YEAR || TimerGameCalendar::year >= ORIGINAL_MAX_YEAR)) return true;
+	if (check_year && (TimerGameCalendar::year < CalendarTime::ORIGINAL_BASE_YEAR || TimerGameCalendar::year >= CalendarTime::ORIGINAL_MAX_YEAR)) return true;
 
 	if (_economy.inflation_prices == MAX_INFLATION || _economy.inflation_payment == MAX_INFLATION) return true;
 
@@ -928,7 +928,7 @@ void StartupEconomy()
 
 	if (_settings_game.economy.inflation) {
 		/* Apply inflation that happened before our game start year. */
-		int months = static_cast<int32_t>(std::min(TimerGameCalendar::year, ORIGINAL_MAX_YEAR) - ORIGINAL_BASE_YEAR) * 12;
+		int months = static_cast<int32_t>(std::min(TimerGameCalendar::year, CalendarTime::ORIGINAL_MAX_YEAR) - CalendarTime::ORIGINAL_BASE_YEAR) * 12;
 		for (int i = 0; i < months; i++) {
 			AddInflation(false);
 		}
diff --git a/src/engine.cpp b/src/engine.cpp
--- a/src/engine.cpp
+++ b/src/engine.cpp
@@ -438,7 +438,7 @@ uint Engine::GetDisplayMaxTractiveEffort
  */
 TimerGameCalendar::Date Engine::GetLifeLengthInDays() const
 {
-	return DateAtStartOfYear(this->info.lifelength + _settings_game.vehicle.extend_vehicle_life);
+	return TimerGameCalendar::DateAtStartOfYear(this->info.lifelength + _settings_game.vehicle.extend_vehicle_life);
 }
 
 /**
@@ -663,7 +663,7 @@ void SetYearEngineAgingStops()
 
 		/* Base year ending date on half the model life */
 		TimerGameCalendar::YearMonthDay ymd;
-		TimerGameCalendar::ConvertDateToYMD(ei->base_intro + static_cast<int32_t>(DateAtStartOfYear(ei->lifelength)) / 2, &ymd);
+		TimerGameCalendar::ConvertDateToYMD(ei->base_intro + static_cast<int32_t>(TimerGameCalendar::DateAtStartOfYear(ei->lifelength)) / 2, &ymd);
 
 		_year_engine_aging_stops = std::max(_year_engine_aging_stops, ymd.year);
 	}
@@ -1103,7 +1103,7 @@ void EnginesMonthlyLoop()
 			/* Do not introduce invalid engines */
 			if (!e->IsEnabled()) continue;
 
-			if (!(e->flags & ENGINE_AVAILABLE) && TimerGameCalendar::date >= (e->intro_date + DAYS_IN_YEAR)) {
+			if (!(e->flags & ENGINE_AVAILABLE) && TimerGameCalendar::date >= (e->intro_date + CalendarTime::DAYS_IN_YEAR)) {
 				/* Introduce it to all companies */
 				NewVehicleAvailable(e);
 			} else if (!(e->flags & (ENGINE_AVAILABLE | ENGINE_EXCLUSIVE_PREVIEW)) && TimerGameCalendar::date >= e->intro_date) {
diff --git a/src/genworld_gui.cpp b/src/genworld_gui.cpp
--- a/src/genworld_gui.cpp
+++ b/src/genworld_gui.cpp
@@ -569,8 +569,8 @@ struct GenerateLandscapeWindow : public 
 			this->SetWidgetDisabledState(WID_GL_HEIGHTMAP_HEIGHT_DOWN, _settings_newgame.game_creation.heightmap_height <= MIN_HEIGHTMAP_HEIGHT);
 			this->SetWidgetDisabledState(WID_GL_HEIGHTMAP_HEIGHT_UP, _settings_newgame.game_creation.heightmap_height >= GetMapHeightLimit());
 		}
-		this->SetWidgetDisabledState(WID_GL_START_DATE_DOWN, _settings_newgame.game_creation.starting_year <= MIN_YEAR);
-		this->SetWidgetDisabledState(WID_GL_START_DATE_UP,   _settings_newgame.game_creation.starting_year >= MAX_YEAR);
+		this->SetWidgetDisabledState(WID_GL_START_DATE_DOWN, _settings_newgame.game_creation.starting_year <= CalendarTime::MIN_YEAR);
+		this->SetWidgetDisabledState(WID_GL_START_DATE_UP,   _settings_newgame.game_creation.starting_year >= CalendarTime::MAX_YEAR);
 		this->SetWidgetDisabledState(WID_GL_SNOW_COVERAGE_DOWN, _settings_newgame.game_creation.snow_coverage <= 0 || _settings_newgame.game_creation.landscape != LT_ARCTIC);
 		this->SetWidgetDisabledState(WID_GL_SNOW_COVERAGE_UP,   _settings_newgame.game_creation.snow_coverage >= 100 || _settings_newgame.game_creation.landscape != LT_ARCTIC);
 		this->SetWidgetDisabledState(WID_GL_DESERT_COVERAGE_DOWN, _settings_newgame.game_creation.desert_coverage <= 0 || _settings_newgame.game_creation.landscape != LT_TROPIC);
@@ -599,7 +599,7 @@ struct GenerateLandscapeWindow : public 
 				break;
 
 			case WID_GL_START_DATE_TEXT:
-				SetDParam(0, TimerGameCalendar::ConvertYMDToDate(MAX_YEAR, 0, 1));
+				SetDParam(0, TimerGameCalendar::ConvertYMDToDate(CalendarTime::MAX_YEAR, 0, 1));
 				d = GetStringBoundingBox(STR_JUST_DATE_LONG);
 				break;
 
@@ -763,7 +763,7 @@ struct GenerateLandscapeWindow : public 
 				if (!(this->flags & WF_TIMEOUT) || this->timeout_timer <= 1) {
 					this->HandleButtonClick(widget);
 
-					_settings_newgame.game_creation.starting_year = Clamp(_settings_newgame.game_creation.starting_year + widget - WID_GL_START_DATE_TEXT, MIN_YEAR, MAX_YEAR);
+					_settings_newgame.game_creation.starting_year = Clamp(_settings_newgame.game_creation.starting_year + widget - WID_GL_START_DATE_TEXT, CalendarTime::MIN_YEAR, CalendarTime::MAX_YEAR);
 					this->InvalidateData();
 				}
 				_left_button_clicked = false;
@@ -968,7 +968,7 @@ struct GenerateLandscapeWindow : public 
 			/* An empty string means revert to the default */
 			switch (this->widget_id) {
 				case WID_GL_HEIGHTMAP_HEIGHT_TEXT: value = MAP_HEIGHT_LIMIT_AUTO_MINIMUM; break;
-				case WID_GL_START_DATE_TEXT: value = static_cast<int32_t>(DEF_START_YEAR); break;
+				case WID_GL_START_DATE_TEXT: value = static_cast<int32_t>(CalendarTime::DEF_START_YEAR); break;
 				case WID_GL_SNOW_COVERAGE_TEXT: value = DEF_SNOW_COVERAGE; break;
 				case WID_GL_DESERT_COVERAGE_TEXT: value = DEF_DESERT_COVERAGE; break;
 				case WID_GL_TOWN_PULLDOWN: value = 1; break;
@@ -987,7 +987,7 @@ struct GenerateLandscapeWindow : public 
 
 			case WID_GL_START_DATE_TEXT:
 				this->SetWidgetDirty(WID_GL_START_DATE_TEXT);
-				_settings_newgame.game_creation.starting_year = Clamp(TimerGameCalendar::Year(value), MIN_YEAR, MAX_YEAR);
+				_settings_newgame.game_creation.starting_year = Clamp(TimerGameCalendar::Year(value), CalendarTime::MIN_YEAR, CalendarTime::MAX_YEAR);
 				break;
 
 			case WID_GL_SNOW_COVERAGE_TEXT:
@@ -1125,8 +1125,8 @@ struct CreateScenarioWindow : public Win
 
 	void OnPaint() override
 	{
-		this->SetWidgetDisabledState(WID_CS_START_DATE_DOWN,       _settings_newgame.game_creation.starting_year <= MIN_YEAR);
-		this->SetWidgetDisabledState(WID_CS_START_DATE_UP,         _settings_newgame.game_creation.starting_year >= MAX_YEAR);
+		this->SetWidgetDisabledState(WID_CS_START_DATE_DOWN,       _settings_newgame.game_creation.starting_year <= CalendarTime::MIN_YEAR);
+		this->SetWidgetDisabledState(WID_CS_START_DATE_UP,         _settings_newgame.game_creation.starting_year >= CalendarTime::MAX_YEAR);
 		this->SetWidgetDisabledState(WID_CS_FLAT_LAND_HEIGHT_DOWN, _settings_newgame.game_creation.se_flat_world_height <= 0);
 		this->SetWidgetDisabledState(WID_CS_FLAT_LAND_HEIGHT_UP,   _settings_newgame.game_creation.se_flat_world_height >= GetMapHeightLimit());
 
@@ -1143,7 +1143,7 @@ struct CreateScenarioWindow : public Win
 		StringID str = STR_JUST_INT;
 		switch (widget) {
 			case WID_CS_START_DATE_TEXT:
-				SetDParam(0, TimerGameCalendar::ConvertYMDToDate(MAX_YEAR, 0, 1));
+				SetDParam(0, TimerGameCalendar::ConvertYMDToDate(CalendarTime::MAX_YEAR, 0, 1));
 				str = STR_JUST_DATE_LONG;
 				break;
 
@@ -1199,7 +1199,7 @@ struct CreateScenarioWindow : public Win
 					this->HandleButtonClick(widget);
 					this->SetDirty();
 
-					_settings_newgame.game_creation.starting_year = Clamp(_settings_newgame.game_creation.starting_year + widget - WID_CS_START_DATE_TEXT, MIN_YEAR, MAX_YEAR);
+					_settings_newgame.game_creation.starting_year = Clamp(_settings_newgame.game_creation.starting_year + widget - WID_CS_START_DATE_TEXT, CalendarTime::MIN_YEAR, CalendarTime::MAX_YEAR);
 				}
 				_left_button_clicked = false;
 				break;
@@ -1258,7 +1258,7 @@ struct CreateScenarioWindow : public Win
 			switch (this->widget_id) {
 				case WID_CS_START_DATE_TEXT:
 					this->SetWidgetDirty(WID_CS_START_DATE_TEXT);
-					_settings_newgame.game_creation.starting_year = Clamp(TimerGameCalendar::Year(value), MIN_YEAR, MAX_YEAR);
+					_settings_newgame.game_creation.starting_year = Clamp(TimerGameCalendar::Year(value), CalendarTime::MIN_YEAR, CalendarTime::MAX_YEAR);
 					break;
 
 				case WID_CS_FLAT_LAND_HEIGHT_TEXT:
diff --git a/src/linkgraph/flowmapper.cpp b/src/linkgraph/flowmapper.cpp
--- a/src/linkgraph/flowmapper.cpp
+++ b/src/linkgraph/flowmapper.cpp
@@ -50,7 +50,7 @@ void FlowMapper::Run(LinkGraphJob &job) 
 			/* Scale by time the graph has been running without being compressed. Add 1 to avoid
 			 * division by 0 if spawn date == last compression date. This matches
 			 * LinkGraph::Monthly(). */
-			auto runtime = job.JoinDate() - job.Settings().recalc_time / SECONDS_PER_DAY - job.LastCompression() + 1;
+			auto runtime = job.JoinDate() - job.Settings().recalc_time / CalendarTime::SECONDS_PER_DAY - job.LastCompression() + 1;
 			for (auto &it : flows) {
 				it.second.ScaleToMonthly(static_cast<int32_t>(runtime));
 			}
diff --git a/src/linkgraph/linkgraph.cpp b/src/linkgraph/linkgraph.cpp
--- a/src/linkgraph/linkgraph.cpp
+++ b/src/linkgraph/linkgraph.cpp
@@ -29,7 +29,7 @@ LinkGraph::BaseNode::BaseNode(TileIndex 
 	this->supply = 0;
 	this->demand = demand;
 	this->station = st;
-	this->last_update = INVALID_DATE;
+	this->last_update = CalendarTime::INVALID_DATE;
 }
 
 /**
@@ -40,8 +40,8 @@ LinkGraph::BaseEdge::BaseEdge(NodeID des
 	this->capacity = 0;
 	this->usage = 0;
 	this->travel_time_sum = 0;
-	this->last_unrestricted_update = INVALID_DATE;
-	this->last_restricted_update = INVALID_DATE;
+	this->last_unrestricted_update = CalendarTime::INVALID_DATE;
+	this->last_restricted_update = CalendarTime::INVALID_DATE;
 	this->dest_node = dest_node;
 }
 
@@ -55,10 +55,10 @@ void LinkGraph::ShiftDates(TimerGameCale
 	this->last_compression += interval;
 	for (NodeID node1 = 0; node1 < this->Size(); ++node1) {
 		BaseNode &source = this->nodes[node1];
-		if (source.last_update != INVALID_DATE) source.last_update += interval;
+		if (source.last_update != CalendarTime::INVALID_DATE) source.last_update += interval;
 		for (BaseEdge &edge : this->nodes[node1].edges) {
-			if (edge.last_unrestricted_update != INVALID_DATE) edge.last_unrestricted_update += interval;
-			if (edge.last_restricted_update != INVALID_DATE) edge.last_restricted_update += interval;
+			if (edge.last_unrestricted_update != CalendarTime::INVALID_DATE) edge.last_unrestricted_update += interval;
+			if (edge.last_restricted_update != CalendarTime::INVALID_DATE) edge.last_restricted_update += interval;
 		}
 	}
 }
diff --git a/src/linkgraph/linkgraph.h b/src/linkgraph/linkgraph.h
--- a/src/linkgraph/linkgraph.h
+++ b/src/linkgraph/linkgraph.h
@@ -63,8 +63,8 @@ public:
 		TimerGameCalendar::Date LastUpdate() const { return std::max(this->last_unrestricted_update, this->last_restricted_update); }
 
 		void Update(uint capacity, uint usage, uint32_t time, EdgeUpdateMode mode);
-		void Restrict() { this->last_unrestricted_update = INVALID_DATE; }
-		void Release() { this->last_restricted_update = INVALID_DATE; }
+		void Restrict() { this->last_unrestricted_update = CalendarTime::INVALID_DATE; }
+		void Release() { this->last_restricted_update = CalendarTime::INVALID_DATE; }
 
 		/** Comparison operator based on \c dest_node. */
 		bool operator <(const BaseEdge &rhs) const
diff --git a/src/linkgraph/linkgraphjob.cpp b/src/linkgraph/linkgraphjob.cpp
--- a/src/linkgraph/linkgraphjob.cpp
+++ b/src/linkgraph/linkgraphjob.cpp
@@ -37,7 +37,7 @@ LinkGraphJob::LinkGraphJob(const LinkGra
 		 * This is on purpose. */
 		link_graph(orig),
 		settings(_settings_game.linkgraph),
-		join_date(TimerGameCalendar::date + (_settings_game.linkgraph.recalc_time / SECONDS_PER_DAY)),
+		join_date(TimerGameCalendar::date + (_settings_game.linkgraph.recalc_time / CalendarTime::SECONDS_PER_DAY)),
 		job_completed(false),
 		job_aborted(false)
 {
@@ -131,14 +131,14 @@ LinkGraphJob::~LinkGraphJob()
 			if (st2 == nullptr || st2->goods[this->Cargo()].link_graph != this->link_graph.index ||
 					st2->goods[this->Cargo()].node != dest_id ||
 					!(*lg)[node_id].HasEdgeTo(dest_id) ||
-					(*lg)[node_id][dest_id].LastUpdate() == INVALID_DATE) {
+					(*lg)[node_id][dest_id].LastUpdate() == CalendarTime::INVALID_DATE) {
 				/* Edge has been removed. Delete flows. */
 				StationIDStack erased = flows.DeleteFlows(to);
 				/* Delete old flows for source stations which have been deleted
 				 * from the new flows. This avoids flow cycles between old and
 				 * new flows. */
 				while (!erased.IsEmpty()) ge.flows.erase(erased.Pop());
-			} else if ((*lg)[node_id][dest_id].last_restricted_update == INVALID_DATE) {
+			} else if ((*lg)[node_id][dest_id].last_restricted_update == CalendarTime::INVALID_DATE) {
 				/* Edge is fully restricted. */
 				flows.RestrictFlows(to);
 			}
diff --git a/src/linkgraph/linkgraphjob.h b/src/linkgraph/linkgraphjob.h
--- a/src/linkgraph/linkgraphjob.h
+++ b/src/linkgraph/linkgraphjob.h
@@ -178,7 +178,7 @@ public:
 	 * settings have to be brutally const-casted in order to populate them.
 	 */
 	LinkGraphJob() : settings(_settings_game.linkgraph),
-			join_date(INVALID_DATE), job_completed(false), job_aborted(false) {}
+			join_date(CalendarTime::INVALID_DATE), job_completed(false), job_aborted(false) {}
 
 	LinkGraphJob(const LinkGraph &orig);
 	~LinkGraphJob();
diff --git a/src/linkgraph/linkgraphschedule.cpp b/src/linkgraph/linkgraphschedule.cpp
--- a/src/linkgraph/linkgraphschedule.cpp
+++ b/src/linkgraph/linkgraphschedule.cpp
@@ -178,7 +178,7 @@ void StateGameLoop_LinkGraphPauseControl
 		}
 	} else if (_pause_mode == PM_UNPAUSED &&
 			TimerGameCalendar::date_fract == LinkGraphSchedule::SPAWN_JOIN_TICK - 2 &&
-			static_cast<int32_t>(TimerGameCalendar::date) % (_settings_game.linkgraph.recalc_interval / SECONDS_PER_DAY) == (_settings_game.linkgraph.recalc_interval / SECONDS_PER_DAY) / 2 &&
+			static_cast<int32_t>(TimerGameCalendar::date) % (_settings_game.linkgraph.recalc_interval / CalendarTime::SECONDS_PER_DAY) == (_settings_game.linkgraph.recalc_interval / CalendarTime::SECONDS_PER_DAY) / 2 &&
 			LinkGraphSchedule::instance.IsJoinWithUnfinishedJobDue()) {
 		/* Perform check two TimerGameCalendar::date_fract ticks before we would join, to make
 		 * sure it also works in multiplayer. */
@@ -205,10 +205,10 @@ void AfterLoad_LinkGraphPauseControl()
 void OnTick_LinkGraph()
 {
 	if (TimerGameCalendar::date_fract != LinkGraphSchedule::SPAWN_JOIN_TICK) return;
-	TimerGameCalendar::Date offset = static_cast<int32_t>(TimerGameCalendar::date) % (_settings_game.linkgraph.recalc_interval / SECONDS_PER_DAY);
+	TimerGameCalendar::Date offset = static_cast<int32_t>(TimerGameCalendar::date) % (_settings_game.linkgraph.recalc_interval / CalendarTime::SECONDS_PER_DAY);
 	if (offset == 0) {
 		LinkGraphSchedule::instance.SpawnNext();
-	} else if (offset == (_settings_game.linkgraph.recalc_interval / SECONDS_PER_DAY) / 2) {
+	} else if (offset == (_settings_game.linkgraph.recalc_interval / CalendarTime::SECONDS_PER_DAY) / 2) {
 		if (!_networking || _network_server) {
 			PerformanceMeasurer::SetInactive(PFE_GL_LINKGRAPH);
 			LinkGraphSchedule::instance.JoinNext();
diff --git a/src/misc_gui.cpp b/src/misc_gui.cpp
--- a/src/misc_gui.cpp
+++ b/src/misc_gui.cpp
@@ -138,7 +138,7 @@ public:
 		/* Because build_date is not set yet in every TileDesc, we make sure it is empty */
 		TileDesc td;
 
-		td.build_date = INVALID_DATE;
+		td.build_date = CalendarTime::INVALID_DATE;
 
 		/* Most tiles have only one owner, but
 		 *  - drivethrough roadstops can be build on town owned roads (up to 2 owners) and
@@ -224,7 +224,7 @@ public:
 		this->landinfo_data.push_back(GetString(STR_LAND_AREA_INFORMATION_LOCAL_AUTHORITY));
 
 		/* Build date */
-		if (td.build_date != INVALID_DATE) {
+		if (td.build_date != CalendarTime::INVALID_DATE) {
 			SetDParam(0, td.build_date);
 			this->landinfo_data.push_back(GetString(STR_LAND_AREA_INFORMATION_BUILD_DATE));
 		}
diff --git a/src/network/core/network_game_info.cpp b/src/network/core/network_game_info.cpp
--- a/src/network/core/network_game_info.cpp
+++ b/src/network/core/network_game_info.cpp
@@ -255,8 +255,6 @@ void SerializeNetworkGameInfo(Packet *p,
  */
 void DeserializeNetworkGameInfo(Packet *p, NetworkGameInfo *info, const GameInfoNewGRFLookupTable *newgrf_lookup_table)
 {
-	static const TimerGameCalendar::Date MAX_DATE = TimerGameCalendar::ConvertYMDToDate(MAX_YEAR, 11, 31); // December is month 11
-
 	byte game_info_version = p->Recv_uint8();
 	NewGRFSerializationType newgrf_serialisation = NST_GRFID_MD5;
 
@@ -323,8 +321,8 @@ void DeserializeNetworkGameInfo(Packet *
 		}
 
 		case 3:
-			info->game_date      = Clamp(p->Recv_uint32(), 0, static_cast<int32_t>(MAX_DATE));
-			info->start_date     = Clamp(p->Recv_uint32(), 0, static_cast<int32_t>(MAX_DATE));
+			info->game_date      = Clamp(p->Recv_uint32(), 0, static_cast<int32_t>(CalendarTime::MAX_DATE));
+			info->start_date     = Clamp(p->Recv_uint32(), 0, static_cast<int32_t>(CalendarTime::MAX_DATE));
 			FALLTHROUGH;
 
 		case 2:
@@ -342,8 +340,8 @@ void DeserializeNetworkGameInfo(Packet *
 			info->clients_on     = p->Recv_uint8 ();
 			info->spectators_on  = p->Recv_uint8 ();
 			if (game_info_version < 3) { // 16 bits dates got scrapped and are read earlier
-				info->game_date    = p->Recv_uint16() + DAYS_TILL_ORIGINAL_BASE_YEAR;
-				info->start_date   = p->Recv_uint16() + DAYS_TILL_ORIGINAL_BASE_YEAR;
+				info->game_date    = p->Recv_uint16() + CalendarTime::DAYS_TILL_ORIGINAL_BASE_YEAR;
+				info->start_date   = p->Recv_uint16() + CalendarTime::DAYS_TILL_ORIGINAL_BASE_YEAR;
 			}
 			if (game_info_version < 6) while (p->Recv_uint8() != 0) {} // Used to contain the map-name.
 			info->map_width      = p->Recv_uint16();
diff --git a/src/newgrf.cpp b/src/newgrf.cpp
--- a/src/newgrf.cpp
+++ b/src/newgrf.cpp
@@ -996,7 +996,7 @@ static ChangeInfoResult CommonVehicleCha
 {
 	switch (prop) {
 		case 0x00: // Introduction date
-			ei->base_intro = buf->ReadWord() + DAYS_TILL_ORIGINAL_BASE_YEAR;
+			ei->base_intro = buf->ReadWord() + CalendarTime::DAYS_TILL_ORIGINAL_BASE_YEAR;
 			break;
 
 		case 0x02: // Decay speed
@@ -2197,7 +2197,7 @@ static ChangeInfoResult BridgeChangeInfo
 			case 0x08: { // Year of availability
 				/* We treat '0' as always available */
 				byte year = buf->ReadByte();
-				bridge->avail_year = (year > 0 ? ORIGINAL_BASE_YEAR + year : 0);
+				bridge->avail_year = (year > 0 ? CalendarTime::ORIGINAL_BASE_YEAR + year : 0);
 				break;
 			}
 
@@ -2257,7 +2257,7 @@ static ChangeInfoResult BridgeChangeInfo
 				break;
 
 			case 0x0F: // Long format year of availability (year since year 0)
-				bridge->avail_year = Clamp(TimerGameCalendar::Year(buf->ReadDWord()), MIN_YEAR, MAX_YEAR);
+				bridge->avail_year = Clamp(TimerGameCalendar::Year(buf->ReadDWord()), CalendarTime::MIN_YEAR, CalendarTime::MAX_YEAR);
 				break;
 
 			case 0x10: { // purchase string
@@ -2430,8 +2430,8 @@ static ChangeInfoResult TownHouseChangeI
 
 			case 0x0A: { // Availability years
 				uint16_t years = buf->ReadWord();
-				housespec->min_year = GB(years, 0, 8) > 150 ? MAX_YEAR : ORIGINAL_BASE_YEAR + GB(years, 0, 8);
-				housespec->max_year = GB(years, 8, 8) > 150 ? MAX_YEAR : ORIGINAL_BASE_YEAR + GB(years, 8, 8);
+				housespec->min_year = GB(years, 0, 8) > 150 ? CalendarTime::MAX_YEAR : CalendarTime::ORIGINAL_BASE_YEAR + GB(years, 0, 8);
+				housespec->max_year = GB(years, 8, 8) > 150 ? CalendarTime::MAX_YEAR : CalendarTime::ORIGINAL_BASE_YEAR + GB(years, 8, 8);
 				break;
 			}
 
@@ -3991,7 +3991,7 @@ static ChangeInfoResult AirportChangeInf
 			case 0x0C:
 				as->min_year = buf->ReadWord();
 				as->max_year = buf->ReadWord();
-				if (as->max_year == 0xFFFF) as->max_year = MAX_YEAR;
+				if (as->max_year == 0xFFFF) as->max_year = CalendarTime::MAX_YEAR;
 				break;
 
 			case 0x0D:
@@ -6512,11 +6512,11 @@ bool GetGlobalVariable(byte param, uint3
 {
 	switch (param) {
 		case 0x00: // current date
-			*value = static_cast<int32_t>(std::max(TimerGameCalendar::date - DAYS_TILL_ORIGINAL_BASE_YEAR, TimerGameCalendar::Date(0)));
+			*value = static_cast<int32_t>(std::max(TimerGameCalendar::date - CalendarTime::DAYS_TILL_ORIGINAL_BASE_YEAR, TimerGameCalendar::Date(0)));
 			return true;
 
 		case 0x01: // current year
-			*value = static_cast<int32_t>(Clamp(TimerGameCalendar::year, ORIGINAL_BASE_YEAR, ORIGINAL_MAX_YEAR) - ORIGINAL_BASE_YEAR);
+			*value = static_cast<int32_t>(Clamp(TimerGameCalendar::year, CalendarTime::ORIGINAL_BASE_YEAR, CalendarTime::ORIGINAL_MAX_YEAR) - CalendarTime::ORIGINAL_BASE_YEAR);
 			return true;
 
 		case 0x02: { // detailed date information: month of year (bit 0-7), day of month (bit 8-12), leap year (bit 15), day of year (bit 16-24)
@@ -7228,7 +7228,7 @@ static uint32_t GetPatchVariable(uint8_t
 {
 	switch (param) {
 		/* start year - 1920 */
-		case 0x0B: return static_cast<int32_t>(std::max(_settings_game.game_creation.starting_year, ORIGINAL_BASE_YEAR) - ORIGINAL_BASE_YEAR);
+		case 0x0B: return static_cast<int32_t>(std::max(_settings_game.game_creation.starting_year, CalendarTime::ORIGINAL_BASE_YEAR) - CalendarTime::ORIGINAL_BASE_YEAR);
 
 		/* freight trains weight factor */
 		case 0x0E: return _settings_game.vehicle.freight_trains;
@@ -9237,7 +9237,7 @@ static bool IsHouseSpecValid(HouseSpec *
  */
 static void EnsureEarlyHouse(HouseZones bitmask)
 {
-	TimerGameCalendar::Year min_year = MAX_YEAR;
+	TimerGameCalendar::Year min_year = CalendarTime::MAX_YEAR;
 
 	for (int i = 0; i < NUM_HOUSES; i++) {
 		HouseSpec *hs = HouseSpec::Get(i);
diff --git a/src/newgrf_airport.cpp b/src/newgrf_airport.cpp
--- a/src/newgrf_airport.cpp
+++ b/src/newgrf_airport.cpp
@@ -212,7 +212,7 @@ void AirportOverrideManager::SetEntitySp
 		case 0x7C: return (this->st->airport.psa != nullptr) ? this->st->airport.psa->GetValue(parameter) : 0;
 
 		case 0xF0: return this->st->facilities;
-		case 0xFA: return ClampTo<uint16_t>(this->st->build_date - DAYS_TILL_ORIGINAL_BASE_YEAR);
+		case 0xFA: return ClampTo<uint16_t>(this->st->build_date - CalendarTime::DAYS_TILL_ORIGINAL_BASE_YEAR);
 	}
 
 	return this->st->GetNewGRFVariable(this->ro, variable, parameter, available);
diff --git a/src/newgrf_engine.cpp b/src/newgrf_engine.cpp
--- a/src/newgrf_engine.cpp
+++ b/src/newgrf_engine.cpp
@@ -767,8 +767,8 @@ static uint32_t VehicleGetVariable(Vehic
 			}
 			return (variable - 0x80) == 0x10 ? ticks : GB(ticks, 8, 8);
 		}
-		case 0x12: return ClampTo<uint16_t>(v->date_of_last_service_newgrf - DAYS_TILL_ORIGINAL_BASE_YEAR);
-		case 0x13: return GB(ClampTo<uint16_t>(v->date_of_last_service_newgrf - DAYS_TILL_ORIGINAL_BASE_YEAR), 8, 8);
+		case 0x12: return ClampTo<uint16_t>(v->date_of_last_service_newgrf - CalendarTime::DAYS_TILL_ORIGINAL_BASE_YEAR);
+		case 0x13: return GB(ClampTo<uint16_t>(v->date_of_last_service_newgrf - CalendarTime::DAYS_TILL_ORIGINAL_BASE_YEAR), 8, 8);
 		case 0x14: return v->GetServiceInterval();
 		case 0x15: return GB(v->GetServiceInterval(), 8, 8);
 		case 0x16: return v->last_station_visited;
@@ -829,7 +829,7 @@ static uint32_t VehicleGetVariable(Vehic
 		case 0x41: return GB(ClampTo<uint16_t>(v->age), 8, 8);
 		case 0x42: return ClampTo<uint16_t>(v->max_age);
 		case 0x43: return GB(ClampTo<uint16_t>(v->max_age), 8, 8);
-		case 0x44: return static_cast<int32_t>(Clamp(v->build_year, ORIGINAL_BASE_YEAR, ORIGINAL_MAX_YEAR) - ORIGINAL_BASE_YEAR);
+		case 0x44: return static_cast<int32_t>(Clamp(v->build_year, CalendarTime::ORIGINAL_BASE_YEAR, CalendarTime::ORIGINAL_MAX_YEAR) - CalendarTime::ORIGINAL_BASE_YEAR);
 		case 0x45: return v->unitnumber;
 		case 0x46: return v->GetEngine()->grf_prop.local_id;
 		case 0x47: return GB(v->GetEngine()->grf_prop.local_id, 8, 8);
@@ -974,9 +974,9 @@ static uint32_t VehicleGetVariable(Vehic
 			case 0x48: return Engine::Get(this->self_type)->flags; // Vehicle Type Info
 			case 0x49: return static_cast<int32_t>(TimerGameCalendar::year); // 'Long' format build year
 			case 0x4B: return static_cast<int32_t>(TimerGameCalendar::date); // Long date of last service
-			case 0x92: return ClampTo<uint16_t>(TimerGameCalendar::date - DAYS_TILL_ORIGINAL_BASE_YEAR); // Date of last service
-			case 0x93: return GB(ClampTo<uint16_t>(TimerGameCalendar::date - DAYS_TILL_ORIGINAL_BASE_YEAR), 8, 8);
-			case 0xC4: return static_cast<int32_t>(Clamp(TimerGameCalendar::year, ORIGINAL_BASE_YEAR, ORIGINAL_MAX_YEAR) - ORIGINAL_BASE_YEAR); // Build year
+			case 0x92: return ClampTo<uint16_t>(TimerGameCalendar::date - CalendarTime::DAYS_TILL_ORIGINAL_BASE_YEAR); // Date of last service
+			case 0x93: return GB(ClampTo<uint16_t>(TimerGameCalendar::date - CalendarTime::DAYS_TILL_ORIGINAL_BASE_YEAR), 8, 8);
+			case 0xC4: return static_cast<int32_t>(Clamp(TimerGameCalendar::year, CalendarTime::ORIGINAL_BASE_YEAR, CalendarTime::ORIGINAL_MAX_YEAR) - CalendarTime::ORIGINAL_BASE_YEAR); // Build year
 			case 0xC6: return Engine::Get(this->self_type)->grf_prop.local_id;
 			case 0xC7: return GB(Engine::Get(this->self_type)->grf_prop.local_id, 8, 8);
 			case 0xDA: return INVALID_VEHICLE; // Next vehicle
diff --git a/src/newgrf_industries.cpp b/src/newgrf_industries.cpp
--- a/src/newgrf_industries.cpp
+++ b/src/newgrf_industries.cpp
@@ -396,16 +396,16 @@ static uint32_t GetCountAndDistanceOfClo
 		case 0xA6: return indspec->grf_prop.local_id;
 		case 0xA7: return this->industry->founder;
 		case 0xA8: return this->industry->random_colour;
-		case 0xA9: return ClampTo<uint8_t>(this->industry->last_prod_year - ORIGINAL_BASE_YEAR);
+		case 0xA9: return ClampTo<uint8_t>(this->industry->last_prod_year - CalendarTime::ORIGINAL_BASE_YEAR);
 		case 0xAA: return this->industry->counter;
 		case 0xAB: return GB(this->industry->counter, 8, 8);
 		case 0xAC: return this->industry->was_cargo_delivered;
 
-		case 0xB0: return ClampTo<uint16_t>(this->industry->construction_date - DAYS_TILL_ORIGINAL_BASE_YEAR); // Date when built since 1920 (in days)
+		case 0xB0: return ClampTo<uint16_t>(this->industry->construction_date - CalendarTime::DAYS_TILL_ORIGINAL_BASE_YEAR); // Date when built since 1920 (in days)
 		case 0xB3: return this->industry->construction_type; // Construction type
 		case 0xB4: {
 			auto it = std::max_element(std::begin(this->industry->accepted), std::end(this->industry->accepted), [](const auto &a, const auto &b) { return a.last_accepted < b.last_accepted; });
-			return ClampTo<uint16_t>(it->last_accepted - DAYS_TILL_ORIGINAL_BASE_YEAR); // Date last cargo accepted since 1920 (in days)
+			return ClampTo<uint16_t>(it->last_accepted - CalendarTime::DAYS_TILL_ORIGINAL_BASE_YEAR); // Date last cargo accepted since 1920 (in days)
 		}
 	}
 
diff --git a/src/newgrf_roadstop.cpp b/src/newgrf_roadstop.cpp
--- a/src/newgrf_roadstop.cpp
+++ b/src/newgrf_roadstop.cpp
@@ -173,7 +173,7 @@ uint32_t RoadStopScopeResolver::GetVaria
 
 		case 0xF0: return this->st == nullptr ? 0 : this->st->facilities; // facilities
 
-		case 0xFA: return ClampTo<uint16_t>((this->st == nullptr ? TimerGameCalendar::date : this->st->build_date) - DAYS_TILL_ORIGINAL_BASE_YEAR); // build date
+		case 0xFA: return ClampTo<uint16_t>((this->st == nullptr ? TimerGameCalendar::date : this->st->build_date) - CalendarTime::DAYS_TILL_ORIGINAL_BASE_YEAR); // build date
 	}
 
 	if (this->st != nullptr) return this->st->GetNewGRFVariable(this->ro, variable, parameter, available);
diff --git a/src/newgrf_station.cpp b/src/newgrf_station.cpp
--- a/src/newgrf_station.cpp
+++ b/src/newgrf_station.cpp
@@ -291,7 +291,7 @@ TownScopeResolver *StationResolverObject
 				}
 				break;
 
-			case 0xFA: return ClampTo<uint16_t>(TimerGameCalendar::date - DAYS_TILL_ORIGINAL_BASE_YEAR); // Build date, clamped to a 16 bit value
+			case 0xFA: return ClampTo<uint16_t>(TimerGameCalendar::date - CalendarTime::DAYS_TILL_ORIGINAL_BASE_YEAR); // Build date, clamped to a 16 bit value
 		}
 
 		*available = false;
@@ -381,7 +381,7 @@ TownScopeResolver *StationResolverObject
 		case 0x84: return this->st->string_id;
 		case 0x86: return 0;
 		case 0xF0: return this->st->facilities;
-		case 0xFA: return ClampTo<uint16_t>(this->st->build_date - DAYS_TILL_ORIGINAL_BASE_YEAR);
+		case 0xFA: return ClampTo<uint16_t>(this->st->build_date - CalendarTime::DAYS_TILL_ORIGINAL_BASE_YEAR);
 	}
 
 	return this->st->GetNewGRFVariable(this->ro, variable, parameter, available);
diff --git a/src/newgrf_text.cpp b/src/newgrf_text.cpp
--- a/src/newgrf_text.cpp
+++ b/src/newgrf_text.cpp
@@ -23,6 +23,7 @@
 #include "newgrf_text.h"
 #include "newgrf_cargo.h"
 #include "string_func.h"
+#include "timer/timer_game_calendar.h"
 #include "date_type.h"
 #include "debug.h"
 #include "core/alloc_type.hpp"
@@ -912,7 +913,7 @@ uint RemapNewGRFStringControlCode(uint s
 
 			/* Dates from NewGRFs have 1920-01-01 as their zero point, convert it to OpenTTD's epoch. */
 			case SCC_NEWGRF_PRINT_WORD_DATE_LONG:
-			case SCC_NEWGRF_PRINT_WORD_DATE_SHORT:  parameters.SetParam(0, _newgrf_textrefstack.PopUnsignedWord() + DAYS_TILL_ORIGINAL_BASE_YEAR); break;
+			case SCC_NEWGRF_PRINT_WORD_DATE_SHORT:  parameters.SetParam(0, _newgrf_textrefstack.PopUnsignedWord() + CalendarTime::DAYS_TILL_ORIGINAL_BASE_YEAR); break;
 
 			case SCC_NEWGRF_DISCARD_WORD:           _newgrf_textrefstack.PopUnsignedWord(); break;
 
diff --git a/src/news_gui.cpp b/src/news_gui.cpp
--- a/src/news_gui.cpp
+++ b/src/news_gui.cpp
@@ -1134,7 +1134,7 @@ struct MessageHistoryWindow : Window {
 
 			/* Months are off-by-one, so it's actually 8. Not using
 			 * month 12 because the 1 is usually less wide. */
-			SetDParam(0, TimerGameCalendar::ConvertYMDToDate(ORIGINAL_MAX_YEAR, 7, 30));
+			SetDParam(0, TimerGameCalendar::ConvertYMDToDate(CalendarTime::ORIGINAL_MAX_YEAR, 7, 30));
 			this->date_width = GetStringBoundingBox(STR_JUST_DATE_TINY).width + WidgetDimensions::scaled.hsep_wide;
 
 			size->height = 4 * resize->height + WidgetDimensions::scaled.framerect.Vertical(); // At least 4 lines are visible.
diff --git a/src/openttd.cpp b/src/openttd.cpp
--- a/src/openttd.cpp
+++ b/src/openttd.cpp
@@ -380,7 +380,7 @@ void OpenBrowser(const char *url)
 
 /** Callback structure of statements to be executed after the NewGRF scan. */
 struct AfterNewGRFScan : NewGRFScanCallback {
-	TimerGameCalendar::Year startyear = INVALID_YEAR; ///< The start year.
+	TimerGameCalendar::Year startyear = CalendarTime::INVALID_YEAR; ///< The start year.
 	uint32_t generation_seed = GENERATE_NEW_SEED; ///< Seed for the new game.
 	std::string dedicated_host;                 ///< Hostname for the dedicated server.
 	uint16_t dedicated_port = 0;                  ///< Port for the dedicated server.
@@ -429,7 +429,7 @@ struct AfterNewGRFScan : NewGRFScanCallb
 		MusicDriver::GetInstance()->SetVolume(_settings_client.music.music_vol);
 		SetEffectVolume(_settings_client.music.effect_vol);
 
-		if (startyear != INVALID_YEAR) IConsoleSetSetting("game_creation.starting_year", static_cast<int32_t>(startyear));
+		if (startyear != CalendarTime::INVALID_YEAR) IConsoleSetSetting("game_creation.starting_year", static_cast<int32_t>(startyear));
 		if (generation_seed != GENERATE_NEW_SEED) _settings_newgame.game_creation.generation_seed = generation_seed;
 
 		if (!dedicated_host.empty()) {
diff --git a/src/order_base.h b/src/order_base.h
--- a/src/order_base.h
+++ b/src/order_base.h
@@ -367,8 +367,8 @@ public:
 	bool IsCompleteTimetable() const;
 
 	/**
-	 * Gets the total duration of the vehicles timetable or Tick::INVALID_TICKS is the timetable is not complete.
-	 * @return total timetable duration or Tick::INVALID_TICKS for incomplete timetables
+	 * Gets the total duration of the vehicles timetable or Ticks::INVALID_TICKS is the timetable is not complete.
+	 * @return total timetable duration or Ticks::INVALID_TICKS for incomplete timetables
 	 */
 	inline TimerGameTick::Ticks GetTimetableTotalDuration() const { return this->IsCompleteTimetable() ? this->timetable_duration : Ticks::INVALID_TICKS; }
 
diff --git a/src/order_cmd.cpp b/src/order_cmd.cpp
--- a/src/order_cmd.cpp
+++ b/src/order_cmd.cpp
@@ -1947,10 +1947,10 @@ VehicleOrderID ProcessConditionalOrder(c
 		case OCV_RELIABILITY:        skip_order = OrderConditionCompare(occ, ToPercent16(v->reliability),       value); break;
 		case OCV_MAX_RELIABILITY:    skip_order = OrderConditionCompare(occ, ToPercent16(v->GetEngine()->reliability),   value); break;
 		case OCV_MAX_SPEED:          skip_order = OrderConditionCompare(occ, v->GetDisplayMaxSpeed() * 10 / 16, value); break;
-		case OCV_AGE:                skip_order = OrderConditionCompare(occ, DateToYear(v->age),                value); break;
+		case OCV_AGE:                skip_order = OrderConditionCompare(occ, TimerGameCalendar::DateToYear(v->age),                value); break;
 		case OCV_REQUIRES_SERVICE:   skip_order = OrderConditionCompare(occ, v->NeedsServicing(),               value); break;
 		case OCV_UNCONDITIONALLY:    skip_order = true; break;
-		case OCV_REMAINING_LIFETIME: skip_order = OrderConditionCompare(occ, std::max(DateToYear(v->max_age - v->age + DAYS_IN_LEAP_YEAR - 1), TimerGameCalendar::Year(0)), value); break;
+		case OCV_REMAINING_LIFETIME: skip_order = OrderConditionCompare(occ, std::max(TimerGameCalendar::DateToYear(v->max_age - v->age + CalendarTime::DAYS_IN_LEAP_YEAR - 1), TimerGameCalendar::Year(0)), value); break;
 		default: NOT_REACHED();
 	}
 
diff --git a/src/rail.cpp b/src/rail.cpp
--- a/src/rail.cpp
+++ b/src/rail.cpp
@@ -225,7 +225,7 @@ RailTypes AddDateIntroducedRailTypes(Rai
 		if (rti->label == 0) continue;
 
 		/* Not date introduced. */
-		if (!IsInsideMM(rti->introduction_date, 0, static_cast<int32_t>(MAX_DATE))) continue;
+		if (!IsInsideMM(rti->introduction_date, 0, static_cast<int32_t>(CalendarTime::MAX_DATE))) continue;
 
 		/* Not yet introduced at this date. */
 		if (rti->introduction_date > date) continue;
@@ -256,7 +256,7 @@ RailTypes GetCompanyRailtypes(CompanyID 
 		const EngineInfo *ei = &e->info;
 
 		if (HasBit(ei->climates, _settings_game.game_creation.landscape) &&
-				(HasBit(e->company_avail, company) || TimerGameCalendar::date >= e->intro_date + DAYS_IN_YEAR)) {
+				(HasBit(e->company_avail, company) || TimerGameCalendar::date >= e->intro_date + CalendarTime::DAYS_IN_YEAR)) {
 			const RailVehicleInfo *rvi = &e->u.rail;
 
 			if (rvi->railveh_type != RAILVEH_WAGON) {
@@ -298,7 +298,7 @@ RailTypes GetRailTypes(bool introduces)
 		}
 	}
 
-	if (introduces) return AddDateIntroducedRailTypes(rts, MAX_DATE);
+	if (introduces) return AddDateIntroducedRailTypes(rts, CalendarTime::MAX_DATE);
 	return rts;
 }
 
diff --git a/src/road.cpp b/src/road.cpp
--- a/src/road.cpp
+++ b/src/road.cpp
@@ -115,7 +115,7 @@ bool HasRoadTypeAvail(const CompanyID co
 		if (rti->label == 0) return false;
 
 		/* Not yet introduced at this date. */
-		if (IsInsideMM(rti->introduction_date, 0, static_cast<int32_t>(MAX_DATE)) && rti->introduction_date > TimerGameCalendar::date) return false;
+		if (IsInsideMM(rti->introduction_date, 0, static_cast<int32_t>(CalendarTime::MAX_DATE)) && rti->introduction_date > TimerGameCalendar::date) return false;
 
 		/*
 		 * Do not allow building hidden road types, except when a town may build it.
@@ -173,7 +173,7 @@ RoadTypes AddDateIntroducedRoadTypes(Roa
 		if (rti->label == 0) continue;
 
 		/* Not date introduced. */
-		if (!IsInsideMM(rti->introduction_date, 0, static_cast<int32_t>(MAX_DATE))) continue;
+		if (!IsInsideMM(rti->introduction_date, 0, static_cast<int32_t>(CalendarTime::MAX_DATE))) continue;
 
 		/* Not yet introduced at this date. */
 		if (rti->introduction_date > date) continue;
@@ -204,7 +204,7 @@ RoadTypes GetCompanyRoadTypes(CompanyID 
 		const EngineInfo *ei = &e->info;
 
 		if (HasBit(ei->climates, _settings_game.game_creation.landscape) &&
-				(HasBit(e->company_avail, company) || TimerGameCalendar::date >= e->intro_date + DAYS_IN_YEAR)) {
+				(HasBit(e->company_avail, company) || TimerGameCalendar::date >= e->intro_date + CalendarTime::DAYS_IN_YEAR)) {
 			const RoadVehicleInfo *rvi = &e->u.road;
 			assert(rvi->roadtype < ROADTYPE_END);
 			if (introduces) {
@@ -241,7 +241,7 @@ RoadTypes GetRoadTypes(bool introduces)
 		}
 	}
 
-	if (introduces) return AddDateIntroducedRoadTypes(rts, MAX_DATE);
+	if (introduces) return AddDateIntroducedRoadTypes(rts, CalendarTime::MAX_DATE);
 	return rts;
 }
 
@@ -302,7 +302,7 @@ RoadTypes ExistingRoadTypes(CompanyID c)
 	}
 
 	/* Get the date introduced roadtypes as well. */
-	known_roadtypes = AddDateIntroducedRoadTypes(known_roadtypes, MAX_DATE);
+	known_roadtypes = AddDateIntroducedRoadTypes(known_roadtypes, CalendarTime::MAX_DATE);
 
 	return known_roadtypes;
 }
diff --git a/src/road_cmd.cpp b/src/road_cmd.cpp
--- a/src/road_cmd.cpp
+++ b/src/road_cmd.cpp
@@ -150,7 +150,7 @@ RoadType AllocateRoadType(RoadTypeLabel 
 			rti->label = label;
 			rti->alternate_labels.clear();
 			rti->flags = ROTFB_NONE;
-			rti->introduction_date = INVALID_DATE;
+			rti->introduction_date = CalendarTime::INVALID_DATE;
 
 			/* Make us compatible with ourself. */
 			rti->powered_roadtypes = (RoadTypes)(1ULL << rt);
diff --git a/src/roadveh_cmd.cpp b/src/roadveh_cmd.cpp
--- a/src/roadveh_cmd.cpp
+++ b/src/roadveh_cmd.cpp
@@ -1720,7 +1720,7 @@ void RoadVehicle::OnNewDay()
 
 	if (this->running_ticks == 0) return;
 
-	CommandCost cost(EXPENSES_ROADVEH_RUN, this->GetRunningCost() * this->running_ticks / (DAYS_IN_YEAR * Ticks::DAY_TICKS));
+	CommandCost cost(EXPENSES_ROADVEH_RUN, this->GetRunningCost() * this->running_ticks / (CalendarTime::DAYS_IN_YEAR * Ticks::DAY_TICKS));
 
 	this->profit_this_year -= cost.GetCost();
 	this->running_ticks = 0;
diff --git a/src/saveload/afterload.cpp b/src/saveload/afterload.cpp
--- a/src/saveload/afterload.cpp
+++ b/src/saveload/afterload.cpp
@@ -259,7 +259,7 @@ static void InitializeWindowsAndCaches()
 		/* For each company, verify (while loading a scenario) that the inauguration date is the current year and set it
 		 * accordingly if it is not the case.  No need to set it on companies that are not been used already,
 		 * thus the MIN_YEAR (which is really nothing more than Zero, initialized value) test */
-		if (_file_to_saveload.abstract_ftype == FT_SCENARIO && c->inaugurated_year != MIN_YEAR) {
+		if (_file_to_saveload.abstract_ftype == FT_SCENARIO && c->inaugurated_year != CalendarTime::MIN_YEAR) {
 			c->inaugurated_year = TimerGameCalendar::year;
 		}
 	}
@@ -776,13 +776,13 @@ bool AfterLoadGame()
 	}
 
 	if (IsSavegameVersionBefore(SLV_ENDING_YEAR)) {
-		_settings_game.game_creation.ending_year = DEF_END_YEAR;
+		_settings_game.game_creation.ending_year = CalendarTime::DEF_END_YEAR;
 	}
 
 	/* Convert linkgraph update settings from days to seconds. */
 	if (IsSavegameVersionBefore(SLV_LINKGRAPH_SECONDS)) {
-		_settings_game.linkgraph.recalc_interval *= SECONDS_PER_DAY;
-		_settings_game.linkgraph.recalc_time     *= SECONDS_PER_DAY;
+		_settings_game.linkgraph.recalc_interval *= CalendarTime::SECONDS_PER_DAY;
+		_settings_game.linkgraph.recalc_time     *= CalendarTime::SECONDS_PER_DAY;
 	}
 
 	/* Load the sprites */
@@ -1422,18 +1422,18 @@ bool AfterLoadGame()
 	/* Time starts at 0 instead of 1920.
 	 * Account for this in older games by adding an offset */
 	if (IsSavegameVersionBefore(SLV_31)) {
-		TimerGameCalendar::date += DAYS_TILL_ORIGINAL_BASE_YEAR;
-		TimerGameCalendar::year += ORIGINAL_BASE_YEAR;
-
-		for (Station *st : Station::Iterate())   st->build_date      += DAYS_TILL_ORIGINAL_BASE_YEAR;
-		for (Waypoint *wp : Waypoint::Iterate()) wp->build_date      += DAYS_TILL_ORIGINAL_BASE_YEAR;
-		for (Engine *e : Engine::Iterate())      e->intro_date       += DAYS_TILL_ORIGINAL_BASE_YEAR;
-		for (Company *c : Company::Iterate()) c->inaugurated_year += ORIGINAL_BASE_YEAR;
-		for (Industry *i : Industry::Iterate())  i->last_prod_year   += ORIGINAL_BASE_YEAR;
+		TimerGameCalendar::date += CalendarTime::DAYS_TILL_ORIGINAL_BASE_YEAR;
+		TimerGameCalendar::year += CalendarTime::ORIGINAL_BASE_YEAR;
+
+		for (Station *st : Station::Iterate())   st->build_date      += CalendarTime::DAYS_TILL_ORIGINAL_BASE_YEAR;
+		for (Waypoint *wp : Waypoint::Iterate()) wp->build_date      += CalendarTime::DAYS_TILL_ORIGINAL_BASE_YEAR;
+		for (Engine *e : Engine::Iterate())      e->intro_date       += CalendarTime::DAYS_TILL_ORIGINAL_BASE_YEAR;
+		for (Company *c : Company::Iterate()) c->inaugurated_year += CalendarTime::ORIGINAL_BASE_YEAR;
+		for (Industry *i : Industry::Iterate())  i->last_prod_year   += CalendarTime::ORIGINAL_BASE_YEAR;
 
 		for (Vehicle *v : Vehicle::Iterate()) {
-			v->date_of_last_service += DAYS_TILL_ORIGINAL_BASE_YEAR;
-			v->build_year += ORIGINAL_BASE_YEAR;
+			v->date_of_last_service += CalendarTime::DAYS_TILL_ORIGINAL_BASE_YEAR;
+			v->build_year += CalendarTime::ORIGINAL_BASE_YEAR;
 		}
 	}
 
@@ -1925,7 +1925,7 @@ bool AfterLoadGame()
 
 			/* Replace "house construction year" with "house age" */
 			if (IsTileType(t, MP_HOUSE) && IsHouseCompleted(t)) {
-				t.m5() = ClampTo<uint8_t>(TimerGameCalendar::year - (t.m5() + ORIGINAL_BASE_YEAR));
+				t.m5() = ClampTo<uint8_t>(TimerGameCalendar::year - (t.m5() + CalendarTime::ORIGINAL_BASE_YEAR));
 			}
 		}
 	}
diff --git a/src/saveload/misc_sl.cpp b/src/saveload/misc_sl.cpp
--- a/src/saveload/misc_sl.cpp
+++ b/src/saveload/misc_sl.cpp
@@ -135,7 +135,7 @@ struct DATEChunkHandler : ChunkHandler {
 		this->LoadCommon(_date_check_desc, _date_check_sl_compat);
 
 		if (IsSavegameVersionBefore(SLV_31)) {
-			_load_check_data.current_date += DAYS_TILL_ORIGINAL_BASE_YEAR;
+			_load_check_data.current_date += CalendarTime::DAYS_TILL_ORIGINAL_BASE_YEAR;
 		}
 	}
 };
diff --git a/src/saveload/oldloader_sl.cpp b/src/saveload/oldloader_sl.cpp
--- a/src/saveload/oldloader_sl.cpp
+++ b/src/saveload/oldloader_sl.cpp
@@ -398,7 +398,7 @@ static bool FixTTOEngines()
 		for (uint i = 0; i < lengthof(_orig_aircraft_vehicle_info); i++, j++) new (GetTempDataEngine(j)) Engine(VEH_AIRCRAFT, i);
 	}
 
-	TimerGameCalendar::Date aging_date = std::min(TimerGameCalendar::date + DAYS_TILL_ORIGINAL_BASE_YEAR, TimerGameCalendar::ConvertYMDToDate(2050, 0, 1));
+	TimerGameCalendar::Date aging_date = std::min(TimerGameCalendar::date + CalendarTime::DAYS_TILL_ORIGINAL_BASE_YEAR, TimerGameCalendar::ConvertYMDToDate(2050, 0, 1));
 
 	for (EngineID i = 0; i < 256; i++) {
 		int oi = ttd_to_tto[i];
@@ -406,11 +406,11 @@ static bool FixTTOEngines()
 
 		if (oi == 255) {
 			/* Default engine is used */
-			TimerGameCalendar::date += DAYS_TILL_ORIGINAL_BASE_YEAR;
+			TimerGameCalendar::date += CalendarTime::DAYS_TILL_ORIGINAL_BASE_YEAR;
 			StartupOneEngine(e, aging_date, 0);
 			CalcEngineReliability(e, false);
-			e->intro_date -= DAYS_TILL_ORIGINAL_BASE_YEAR;
-			TimerGameCalendar::date -= DAYS_TILL_ORIGINAL_BASE_YEAR;
+			e->intro_date -= CalendarTime::DAYS_TILL_ORIGINAL_BASE_YEAR;
+			TimerGameCalendar::date -= CalendarTime::DAYS_TILL_ORIGINAL_BASE_YEAR;
 
 			/* Make sure for example monorail and maglev are available when they should be */
 			if (TimerGameCalendar::date >= e->intro_date && HasBit(e->info.climates, 0)) {
@@ -1020,7 +1020,7 @@ static bool LoadOldCompany(LoadgameState
 	}
 
 	_company_colours[num] = (Colours)c->colour;
-	c->inaugurated_year -= ORIGINAL_BASE_YEAR;
+	c->inaugurated_year -= CalendarTime::ORIGINAL_BASE_YEAR;
 
 	return true;
 }
diff --git a/src/script/api/script_date.cpp b/src/script/api/script_date.cpp
--- a/src/script/api/script_date.cpp
+++ b/src/script/api/script_date.cpp
@@ -56,7 +56,7 @@
 {
 	if (month < 1 || month > 12) return DATE_INVALID;
 	if (day_of_month < 1 || day_of_month > 31) return DATE_INVALID;
-	if (year < 0 || year > MAX_YEAR) return DATE_INVALID;
+	if (year < 0 || year > CalendarTime::MAX_YEAR) return DATE_INVALID;
 
 	return (ScriptDate::Date)(int32_t)::TimerGameCalendar::ConvertYMDToDate(year, month - 1, day_of_month);
 }
diff --git a/src/script/api/script_date.hpp b/src/script/api/script_date.hpp
--- a/src/script/api/script_date.hpp
+++ b/src/script/api/script_date.hpp
@@ -11,6 +11,7 @@
 #define SCRIPT_DATE_HPP
 
 #include "script_object.hpp"
+#include "timer/timer_game_calendar.h"
 #include "../../date_type.h"
 
 /**
@@ -31,7 +32,7 @@ public:
 	 * compose valid date values for a known year, month and day.
 	 */
 	enum Date {
-		DATE_INVALID = (int32_t)::INVALID_DATE, ///< A value representing an invalid date.
+		DATE_INVALID = (int32_t)::CalendarTime::INVALID_DATE, ///< A value representing an invalid date.
 	};
 
 	/**
diff --git a/src/settings.cpp b/src/settings.cpp
--- a/src/settings.cpp
+++ b/src/settings.cpp
@@ -1283,8 +1283,8 @@ void LoadFromConfig(bool startup)
 	/* Load basic settings only during bootstrap, load other settings not during bootstrap */
 	if (!startup) {
 		if (generic_version < IFV_LINKGRAPH_SECONDS) {
-			_settings_newgame.linkgraph.recalc_interval *= SECONDS_PER_DAY;
-			_settings_newgame.linkgraph.recalc_time     *= SECONDS_PER_DAY;
+			_settings_newgame.linkgraph.recalc_interval *= CalendarTime::SECONDS_PER_DAY;
+			_settings_newgame.linkgraph.recalc_time     *= CalendarTime::SECONDS_PER_DAY;
 		}
 
 		/* Move no_http_content_downloads and use_relay_service from generic_ini to private_ini. */
diff --git a/src/settings_gui.cpp b/src/settings_gui.cpp
--- a/src/settings_gui.cpp
+++ b/src/settings_gui.cpp
@@ -2751,7 +2751,7 @@ struct CustomCurrencyWindow : Window {
 		this->SetWidgetDisabledState(WID_CC_RATE_DOWN, _custom_currency.rate == 1);
 		this->SetWidgetDisabledState(WID_CC_RATE_UP, _custom_currency.rate == UINT16_MAX);
 		this->SetWidgetDisabledState(WID_CC_YEAR_DOWN, _custom_currency.to_euro == CF_NOEURO);
-		this->SetWidgetDisabledState(WID_CC_YEAR_UP, _custom_currency.to_euro == MAX_YEAR);
+		this->SetWidgetDisabledState(WID_CC_YEAR_UP, _custom_currency.to_euro == CalendarTime::MAX_YEAR);
 	}
 
 	void SetStringParameters(int widget) const override
@@ -2850,8 +2850,8 @@ struct CustomCurrencyWindow : Window {
 				break;
 
 			case WID_CC_YEAR_UP:
-				_custom_currency.to_euro = Clamp(_custom_currency.to_euro + 1, MIN_EURO_YEAR, MAX_YEAR);
-				if (_custom_currency.to_euro == MAX_YEAR) this->DisableWidget(WID_CC_YEAR_UP);
+				_custom_currency.to_euro = Clamp(_custom_currency.to_euro + 1, MIN_EURO_YEAR, CalendarTime::MAX_YEAR);
+				if (_custom_currency.to_euro == CalendarTime::MAX_YEAR) this->DisableWidget(WID_CC_YEAR_UP);
 				this->EnableWidget(WID_CC_YEAR_DOWN);
 				break;
 
@@ -2897,7 +2897,7 @@ struct CustomCurrencyWindow : Window {
 			case WID_CC_YEAR: { // Year to switch to euro
 				TimerGameCalendar::Year val = atoi(str);
 
-				_custom_currency.to_euro = (val < MIN_EURO_YEAR ? CF_NOEURO : std::min(val, MAX_YEAR));
+				_custom_currency.to_euro = (val < MIN_EURO_YEAR ? CF_NOEURO : std::min(val, CalendarTime::MAX_YEAR));
 				break;
 			}
 		}
diff --git a/src/ship_cmd.cpp b/src/ship_cmd.cpp
--- a/src/ship_cmd.cpp
+++ b/src/ship_cmd.cpp
@@ -236,7 +236,7 @@ void Ship::OnNewDay()
 
 	if (this->running_ticks == 0) return;
 
-	CommandCost cost(EXPENSES_SHIP_RUN, this->GetRunningCost() * this->running_ticks / (DAYS_IN_YEAR * Ticks::DAY_TICKS));
+	CommandCost cost(EXPENSES_SHIP_RUN, this->GetRunningCost() * this->running_ticks / (CalendarTime::DAYS_IN_YEAR * Ticks::DAY_TICKS));
 
 	this->profit_this_year -= cost.GetCost();
 	this->running_ticks = 0;
diff --git a/src/station.cpp b/src/station.cpp
--- a/src/station.cpp
+++ b/src/station.cpp
@@ -105,7 +105,7 @@ Station::~Station()
 		for (NodeID node = 0; node < lg->Size(); ++node) {
 			Station *st = Station::Get((*lg)[node].station);
 			st->goods[c].flows.erase(this->index);
-			if ((*lg)[node].HasEdgeTo(this->goods[c].node) && (*lg)[node][this->goods[c].node].LastUpdate() != INVALID_DATE) {
+			if ((*lg)[node].HasEdgeTo(this->goods[c].node) && (*lg)[node][this->goods[c].node].LastUpdate() != CalendarTime::INVALID_DATE) {
 				st->goods[c].flows.DeleteFlows(this->index);
 				RerouteCargo(st, c, this->index, st->index);
 			}
diff --git a/src/station_cmd.cpp b/src/station_cmd.cpp
--- a/src/station_cmd.cpp
+++ b/src/station_cmd.cpp
@@ -3863,11 +3863,11 @@ void DeleteStaleLinks(Station *from)
 					ge.flows.DeleteFlows(to->index);
 					RerouteCargo(from, c, to->index, from->index);
 				}
-			} else if (edge.last_unrestricted_update != INVALID_DATE && TimerGameCalendar::date - edge.last_unrestricted_update > timeout) {
+			} else if (edge.last_unrestricted_update != CalendarTime::INVALID_DATE && TimerGameCalendar::date - edge.last_unrestricted_update > timeout) {
 				edge.Restrict();
 				ge.flows.RestrictFlows(to->index);
 				RerouteCargo(from, c, to->index, from->index);
-			} else if (edge.last_restricted_update != INVALID_DATE && TimerGameCalendar::date - edge.last_restricted_update > timeout) {
+			} else if (edge.last_restricted_update != CalendarTime::INVALID_DATE && TimerGameCalendar::date - edge.last_restricted_update > timeout) {
 				edge.Release();
 			}
 		}
diff --git a/src/statusbar_gui.cpp b/src/statusbar_gui.cpp
--- a/src/statusbar_gui.cpp
+++ b/src/statusbar_gui.cpp
@@ -89,7 +89,7 @@ struct StatusBarWindow : Window {
 		Dimension d;
 		switch (widget) {
 			case WID_S_LEFT:
-				SetDParamMaxValue(0, DateAtStartOfYear(MAX_YEAR));
+				SetDParamMaxValue(0, TimerGameCalendar::DateAtStartOfYear(CalendarTime::MAX_YEAR));
 				d = GetStringBoundingBox(STR_JUST_DATE_LONG);
 				break;
 
diff --git a/src/story_gui.cpp b/src/story_gui.cpp
--- a/src/story_gui.cpp
+++ b/src/story_gui.cpp
@@ -699,7 +699,7 @@ public:
 		int y_offset = -scrollpos;
 
 		/* Date */
-		if (page->date != INVALID_DATE) {
+		if (page->date != CalendarTime::INVALID_DATE) {
 			SetDParam(0, page->date);
 			DrawString(0, fr.right, y_offset, STR_JUST_DATE_LONG, TC_BLACK);
 		}
diff --git a/src/subsidy.cpp b/src/subsidy.cpp
--- a/src/subsidy.cpp
+++ b/src/subsidy.cpp
@@ -45,7 +45,7 @@ void Subsidy::AwardTo(CompanyID company)
 	assert(!this->IsAwarded());
 
 	this->awarded = company;
-	this->remaining = _settings_game.difficulty.subsidy_duration * MONTHS_IN_YEAR;
+	this->remaining = _settings_game.difficulty.subsidy_duration * CalendarTime::MONTHS_IN_YEAR;
 
 	SetDParam(0, company);
 	NewsStringData *company_name = new NewsStringData(GetString(STR_COMPANY_NAME));
diff --git a/src/table/airport_defaults.h b/src/table/airport_defaults.h
--- a/src/table/airport_defaults.h
+++ b/src/table/airport_defaults.h
@@ -10,7 +10,7 @@
 #ifndef AIRPORT_DEFAULTS_H
 #define AIRPORT_DEFAULTS_H
 
-#include "date_type.h"
+#include "timer/timer_game_calendar.h"
 
 /**
  * Definition of an airport tiles layout.
@@ -397,20 +397,20 @@ static const Direction _default_airports
 /* The helidepot and helistation have ATP_TTDP_SMALL because they are at ground level */
 extern const AirportSpec _origin_airport_specs[] = {
 	AS(country,          4, 3,     0,     1959,  4,  3,  7, ATP_TTDP_SMALL,    APC_SMALL,    STR_AIRPORT_SMALL,            SPR_AIRPORT_PREVIEW_SMALL),
-	AS(city,             6, 6,  1955, MAX_YEAR,  5,  5, 24, ATP_TTDP_LARGE,    APC_LARGE,    STR_AIRPORT_CITY,             SPR_AIRPORT_PREVIEW_LARGE),
-	AS_ND(heliport,      1, 1,  1963, MAX_YEAR,  4,  1,  4, ATP_TTDP_HELIPORT, APC_HELIPORT, STR_AIRPORT_HELIPORT,         SPR_AIRPORT_PREVIEW_HELIPORT),
-	AS(metropolitan,     6, 6,  1980, MAX_YEAR,  6,  8, 28, ATP_TTDP_LARGE,    APC_LARGE,    STR_AIRPORT_METRO,            SPR_AIRPORT_PREVIEW_METROPOLITAN),
-	AS(international,    7, 7,  1990, MAX_YEAR,  8, 17, 42, ATP_TTDP_LARGE,    APC_HUB,      STR_AIRPORT_INTERNATIONAL,    SPR_AIRPORT_PREVIEW_INTERNATIONAL),
-	AS(commuter,         5, 4,  1983, MAX_YEAR,  4,  4, 20, ATP_TTDP_SMALL,    APC_SMALL,    STR_AIRPORT_COMMUTER,         SPR_AIRPORT_PREVIEW_COMMUTER),
-	AS(helidepot,        2, 2,  1976, MAX_YEAR,  4,  2,  7, ATP_TTDP_SMALL,    APC_HELIPORT, STR_AIRPORT_HELIDEPOT,        SPR_AIRPORT_PREVIEW_HELIDEPOT),
-	AS(intercontinental, 9, 11, 2002, MAX_YEAR, 10, 25, 72, ATP_TTDP_LARGE,    APC_HUB,      STR_AIRPORT_INTERCONTINENTAL, SPR_AIRPORT_PREVIEW_INTERCONTINENTAL),
-	AS(helistation,      4, 2,  1980, MAX_YEAR,  4,  3, 14, ATP_TTDP_SMALL,    APC_HELIPORT, STR_AIRPORT_HELISTATION,      SPR_AIRPORT_PREVIEW_HELISTATION),
+	AS(city,             6, 6,  1955, CalendarTime::MAX_YEAR,  5,  5, 24, ATP_TTDP_LARGE,    APC_LARGE,    STR_AIRPORT_CITY,             SPR_AIRPORT_PREVIEW_LARGE),
+	AS_ND(heliport,      1, 1,  1963, CalendarTime::MAX_YEAR,  4,  1,  4, ATP_TTDP_HELIPORT, APC_HELIPORT, STR_AIRPORT_HELIPORT,         SPR_AIRPORT_PREVIEW_HELIPORT),
+	AS(metropolitan,     6, 6,  1980, CalendarTime::MAX_YEAR,  6,  8, 28, ATP_TTDP_LARGE,    APC_LARGE,    STR_AIRPORT_METRO,            SPR_AIRPORT_PREVIEW_METROPOLITAN),
+	AS(international,    7, 7,  1990, CalendarTime::MAX_YEAR,  8, 17, 42, ATP_TTDP_LARGE,    APC_HUB,      STR_AIRPORT_INTERNATIONAL,    SPR_AIRPORT_PREVIEW_INTERNATIONAL),
+	AS(commuter,         5, 4,  1983, CalendarTime::MAX_YEAR,  4,  4, 20, ATP_TTDP_SMALL,    APC_SMALL,    STR_AIRPORT_COMMUTER,         SPR_AIRPORT_PREVIEW_COMMUTER),
+	AS(helidepot,        2, 2,  1976, CalendarTime::MAX_YEAR,  4,  2,  7, ATP_TTDP_SMALL,    APC_HELIPORT, STR_AIRPORT_HELIDEPOT,        SPR_AIRPORT_PREVIEW_HELIDEPOT),
+	AS(intercontinental, 9, 11, 2002, CalendarTime::MAX_YEAR, 10, 25, 72, ATP_TTDP_LARGE,    APC_HUB,      STR_AIRPORT_INTERCONTINENTAL, SPR_AIRPORT_PREVIEW_INTERCONTINENTAL),
+	AS(helistation,      4, 2,  1980, CalendarTime::MAX_YEAR,  4,  3, 14, ATP_TTDP_SMALL,    APC_HELIPORT, STR_AIRPORT_HELISTATION,      SPR_AIRPORT_PREVIEW_HELISTATION),
 	AS_GENERIC(&_airportfta_oilrig, nullptr, _default_airports_rotation, 0, nullptr, 0, 1, 1, 0, 4, 0, 0, 0, ATP_TTDP_OILRIG, APC_HELIPORT, STR_NULL, 0, false),
 };
 
 static_assert(NEW_AIRPORT_OFFSET == lengthof(_origin_airport_specs));
 
-const AirportSpec AirportSpec::dummy = AS_GENERIC(&_airportfta_dummy, nullptr, _default_airports_rotation, 0, nullptr, 0, 0, 0, 0, 0, MIN_YEAR, MIN_YEAR, 0, ATP_TTDP_LARGE, APC_BEGIN, STR_NULL, 0, false);
+const AirportSpec AirportSpec::dummy = AS_GENERIC(&_airportfta_dummy, nullptr, _default_airports_rotation, 0, nullptr, 0, 0, 0, 0, 0, CalendarTime::MIN_YEAR, CalendarTime::MIN_YEAR, 0, ATP_TTDP_LARGE, APC_BEGIN, STR_NULL, 0, false);
 
 #undef AS
 #undef AS_ND
diff --git a/src/table/engines.h b/src/table/engines.h
--- a/src/table/engines.h
+++ b/src/table/engines.h
@@ -24,7 +24,7 @@
  * @param f Bitmask of the climates
  * @note the 5 between b and f is the load amount
  */
-#define MT(a, b, c, d, e, f) { DAYS_TILL_ORIGINAL_BASE_YEAR + a, c, d, b, 5, f, e, 0, 8, 0, 0, 0, STR_EMPTY, Ticks::CARGO_AGING_TICKS, INVALID_ENGINE, ExtraEngineFlags::None }
+#define MT(a, b, c, d, e, f) { CalendarTime::DAYS_TILL_ORIGINAL_BASE_YEAR + a, c, d, b, 5, f, e, 0, 8, 0, 0, 0, STR_EMPTY, Ticks::CARGO_AGING_TICKS, INVALID_ENGINE, ExtraEngineFlags::None }
 
 /**
  * Writes the properties of a multiple-unit train into the EngineInfo struct.
@@ -37,7 +37,7 @@
  * @param f Bitmask of the climates
  * @note the 5 between b and f is the load amount
  */
-#define MM(a, b, c, d, e, f) { DAYS_TILL_ORIGINAL_BASE_YEAR + a, c, d, b, 5, f, e, 0, 8, 1 << EF_RAIL_IS_MU, 0, 0, STR_EMPTY, Tick::CARGO_AGING_TICKS, INVALID_ENGINE, ExtraEngineFlags::None }
+#define MM(a, b, c, d, e, f) { CalendarTime::DAYS_TILL_ORIGINAL_BASE_YEAR + a, c, d, b, 5, f, e, 0, 8, 1 << EF_RAIL_IS_MU, 0, 0, STR_EMPTY, Ticks::CARGO_AGING_TICKS, INVALID_ENGINE, ExtraEngineFlags::None }
 
 /**
  * Writes the properties of a train carriage into the EngineInfo struct.
@@ -50,7 +50,7 @@
  * @see MT
  * @note the 5 between b and f is the load amount
  */
-#define MW(a, b, c, d, e, f) { DAYS_TILL_ORIGINAL_BASE_YEAR + a, c, d, b, 5, f, e, 0, 8, 0, 0, 0, STR_EMPTY, Tick::CARGO_AGING_TICKS, INVALID_ENGINE, ExtraEngineFlags::None }
+#define MW(a, b, c, d, e, f) { CalendarTime::DAYS_TILL_ORIGINAL_BASE_YEAR + a, c, d, b, 5, f, e, 0, 8, 0, 0, 0, STR_EMPTY, Ticks::CARGO_AGING_TICKS, INVALID_ENGINE, ExtraEngineFlags::None }
 
 /**
  * Writes the properties of a road vehicle into the EngineInfo struct.
@@ -63,7 +63,7 @@
  * @param f Bitmask of the climates
  * @note the 5 between b and f is the load amount
  */
-#define MR(a, b, c, d, e, f) { DAYS_TILL_ORIGINAL_BASE_YEAR + a, c, d, b, 5, f, e, 0, 8, 0, 0, 0, STR_EMPTY, Tick::CARGO_AGING_TICKS, INVALID_ENGINE, ExtraEngineFlags::None }
+#define MR(a, b, c, d, e, f) { CalendarTime::DAYS_TILL_ORIGINAL_BASE_YEAR + a, c, d, b, 5, f, e, 0, 8, 0, 0, 0, STR_EMPTY, Ticks::CARGO_AGING_TICKS, INVALID_ENGINE, ExtraEngineFlags::None }
 
 /**
  * Writes the properties of a ship into the EngineInfo struct.
@@ -75,7 +75,7 @@
  * @param f Bitmask of the climates
  * @note the 10 between b and f is the load amount
  */
-#define MS(a, b, c, d, e, f) { DAYS_TILL_ORIGINAL_BASE_YEAR + a, c, d, b, 10, f, e, 0, 8, 0, 0, 0, STR_EMPTY, Tick::CARGO_AGING_TICKS, INVALID_ENGINE, ExtraEngineFlags::None }
+#define MS(a, b, c, d, e, f) { CalendarTime::DAYS_TILL_ORIGINAL_BASE_YEAR + a, c, d, b, 10, f, e, 0, 8, 0, 0, 0, STR_EMPTY, Ticks::CARGO_AGING_TICKS, INVALID_ENGINE, ExtraEngineFlags::None }
 
 /**
  * Writes the properties of an aeroplane into the EngineInfo struct.
@@ -86,7 +86,7 @@
  * @param e Bitmask of the climates
  * @note the 20 between b and e is the load amount
  */
-#define MA(a, b, c, d, e) { DAYS_TILL_ORIGINAL_BASE_YEAR + a, c, d, b, 20, e, CT_INVALID, 0, 8, 0, 0, 0, STR_EMPTY, Tick::CARGO_AGING_TICKS, INVALID_ENGINE, ExtraEngineFlags::None }
+#define MA(a, b, c, d, e) { CalendarTime::DAYS_TILL_ORIGINAL_BASE_YEAR + a, c, d, b, 20, e, CT_INVALID, 0, 8, 0, 0, 0, STR_EMPTY, Ticks::CARGO_AGING_TICKS, INVALID_ENGINE, ExtraEngineFlags::None }
 
 /* Climates
  * T = Temperate
diff --git a/src/table/object_land.h b/src/table/object_land.h
--- a/src/table/object_land.h
+++ b/src/table/object_land.h
@@ -121,7 +121,7 @@ static const DrawTileSprites _object_hq[
 
 #undef TILE_SPRITE_LINE
 
-#define M(name, size, build_cost_multiplier, clear_cost_multiplier, height, climate, gen_amount, flags) { GRFFilePropsBase<2>(), {0, 0, 0, 0}, INVALID_OBJECT_CLASS, name, climate, size, build_cost_multiplier, clear_cost_multiplier, 0, MAX_DATE + 1, flags, 0, height, 1, gen_amount }
+#define M(name, size, build_cost_multiplier, clear_cost_multiplier, height, climate, gen_amount, flags) { GRFFilePropsBase<2>(), {0, 0, 0, 0}, INVALID_OBJECT_CLASS, name, climate, size, build_cost_multiplier, clear_cost_multiplier, 0, CalendarTime::MAX_DATE + 1, flags, 0, height, 1, gen_amount }
 
 /* Climates
  * T = Temperate
diff --git a/src/table/railtypes.h b/src/table/railtypes.h
--- a/src/table/railtypes.h
+++ b/src/table/railtypes.h
@@ -99,7 +99,7 @@ static const RailtypeInfo _original_rail
 		0x0A,
 
 		/* introduction date */
-		INVALID_DATE,
+		CalendarTime::INVALID_DATE,
 
 		/* railtypes required for this to be introduced */
 		RAILTYPES_NONE,
@@ -200,7 +200,7 @@ static const RailtypeInfo _original_rail
 		0x0A,
 
 		/* introduction date */
-		INVALID_DATE,
+		CalendarTime::INVALID_DATE,
 
 		/* railtypes required for this to be introduced */
 		RAILTYPES_NONE,
@@ -297,7 +297,7 @@ static const RailtypeInfo _original_rail
 		0x0A,
 
 		/* introduction date */
-		INVALID_DATE,
+		CalendarTime::INVALID_DATE,
 
 		/* railtypes required for this to be introduced */
 		RAILTYPES_NONE,
@@ -394,7 +394,7 @@ static const RailtypeInfo _original_rail
 		0x0A,
 
 		/* introduction date */
-		INVALID_DATE,
+		CalendarTime::INVALID_DATE,
 
 		/* railtypes required for this to be introduced */
 		RAILTYPES_NONE,
diff --git a/src/table/roadtypes.h b/src/table/roadtypes.h
--- a/src/table/roadtypes.h
+++ b/src/table/roadtypes.h
@@ -82,7 +82,7 @@ static const RoadTypeInfo _original_road
 		0x01,
 
 		/* introduction date */
-		static_cast<int32_t>(MIN_YEAR),
+		static_cast<int32_t>(CalendarTime::MIN_YEAR),
 
 		/* roadtypes required for this to be introduced */
 		ROADTYPES_NONE,
@@ -162,7 +162,7 @@ static const RoadTypeInfo _original_road
 		0x01,
 
 		/* introduction date */
-		INVALID_DATE,
+		CalendarTime::INVALID_DATE,
 
 		/* roadtypes required for this to be introduced */
 		ROADTYPES_NONE,
diff --git a/src/table/settings/currency_settings.ini b/src/table/settings/currency_settings.ini
--- a/src/table/settings/currency_settings.ini
+++ b/src/table/settings/currency_settings.ini
@@ -50,8 +50,8 @@ cat      = SC_BASIC
 var      = to_euro
 type     = SLE_INT32
 def      = 0
-min      = MIN_YEAR
-max      = MAX_YEAR
+min      = CalendarTime::MIN_YEAR
+max      = CalendarTime::MAX_YEAR
 
 [SDT_SSTR]
 var      = prefix
diff --git a/src/table/settings/gui_settings.ini b/src/table/settings/gui_settings.ini
--- a/src/table/settings/gui_settings.ini
+++ b/src/table/settings/gui_settings.ini
@@ -496,8 +496,8 @@ var      = gui.coloured_news_year
 type     = SLE_INT32
 flags    = SF_NOT_IN_SAVE | SF_NO_NETWORK_SYNC
 def      = 2000
-min      = MIN_YEAR
-max      = MAX_YEAR
+min      = CalendarTime::MIN_YEAR
+max      = CalendarTime::MAX_YEAR
 interval = 1
 str      = STR_CONFIG_SETTING_COLOURED_NEWS_YEAR
 strhelp  = STR_CONFIG_SETTING_COLOURED_NEWS_YEAR_HELPTEXT
@@ -543,8 +543,8 @@ var      = gui.semaphore_build_before
 type     = SLE_INT32
 flags    = SF_NOT_IN_SAVE | SF_NO_NETWORK_SYNC
 def      = 1950
-min      = MIN_YEAR
-max      = MAX_YEAR
+min      = CalendarTime::MIN_YEAR
+max      = CalendarTime::MAX_YEAR
 interval = 1
 str      = STR_CONFIG_SETTING_SEMAPHORE_BUILD_BEFORE_DATE
 strhelp  = STR_CONFIG_SETTING_SEMAPHORE_BUILD_BEFORE_DATE_HELPTEXT
diff --git a/src/table/settings/network_settings.ini b/src/table/settings/network_settings.ini
--- a/src/table/settings/network_settings.ini
+++ b/src/table/settings/network_settings.ini
@@ -237,8 +237,8 @@ var      = network.restart_game_year
 type     = SLE_INT32
 flags    = SF_NOT_IN_SAVE | SF_NO_NETWORK_SYNC | SF_GUI_0_IS_SPECIAL | SF_NETWORK_ONLY
 def      = 0
-min      = MIN_YEAR
-max      = MAX_YEAR
+min      = CalendarTime::MIN_YEAR
+max      = CalendarTime::MAX_YEAR
 interval = 1
 
 [SDTC_VAR]
diff --git a/src/table/settings/world_settings.ini b/src/table/settings/world_settings.ini
--- a/src/table/settings/world_settings.ini
+++ b/src/table/settings/world_settings.ini
@@ -122,9 +122,9 @@ cat      = SC_BASIC
 [SDT_VAR]
 var      = game_creation.starting_year
 type     = SLE_INT32
-def      = DEF_START_YEAR
-min      = MIN_YEAR
-max      = MAX_YEAR
+def      = CalendarTime::DEF_START_YEAR
+min      = CalendarTime::MIN_YEAR
+max      = CalendarTime::MAX_YEAR
 interval = 1
 str      = STR_CONFIG_SETTING_STARTING_YEAR
 strval   = STR_JUST_INT
@@ -135,9 +135,9 @@ var      = game_creation.ending_year
 type     = SLE_INT32
 from     = SLV_ENDING_YEAR
 flags    = SF_GUI_0_IS_SPECIAL
-def      = DEF_END_YEAR
-min      = MIN_YEAR
-max      = MAX_YEAR - 1
+def      = CalendarTime::DEF_END_YEAR
+min      = CalendarTime::MIN_YEAR
+max      = CalendarTime::MAX_YEAR - 1
 interval = 1
 str      = STR_CONFIG_SETTING_ENDING_YEAR
 strhelp  = STR_CONFIG_SETTING_ENDING_YEAR_HELPTEXT
diff --git a/src/table/town_land.h b/src/table/town_land.h
--- a/src/table/town_land.h
+++ b/src/table/town_land.h
@@ -1821,7 +1821,7 @@ static const HouseSpec _original_house_s
 	 *                                                                              remove_rating_decrease
 	 *                                                                              |    mail_generation
 	 *     min_year                                                                 |    |    1st CargoID acceptance
-	 *     |         max_year                                                       |    |    |    2nd CargoID acceptance
+	 *     |         CalendarTime::MAX_YEAR                                                       |    |    |    2nd CargoID acceptance
 	 *     |         |    population                                                |    |    |    |    3th CargoID acceptance
 	 *     |         |    |    removal_cost                                         |    |    |    |    |
 	 *     |         |    |    |    building_name                                   |    |    |    |    |
@@ -1832,59 +1832,59 @@ static const HouseSpec _original_house_s
 	 * +-cargoID accepted |    |    |                                               |    |    |    |    |
 	 * |   |         |    |    |    |                                               |    |    |    |    |
 	 */
-	MS(1963, MAX_YEAR, 187, 150, STR_TOWN_BUILDING_NAME_TALL_OFFICE_BLOCK_1,      140,  70,   8,   3,   4,
+	MS(1963, CalendarTime::MAX_YEAR, 187, 150, STR_TOWN_BUILDING_NAME_TALL_OFFICE_BLOCK_1,      140,  70,   8,   3,   4,
 	   TILE_SIZE_1x1,
 	   HZ_TEMP | HZ_ZON5,
 	   CT_PASSENGERS, CT_MAIL, CT_GOODS), // 00
-	MS(1957, MAX_YEAR,  85, 140, STR_TOWN_BUILDING_NAME_OFFICE_BLOCK_1,           130,  55,   8,   3,   4,
+	MS(1957, CalendarTime::MAX_YEAR,  85, 140, STR_TOWN_BUILDING_NAME_OFFICE_BLOCK_1,           130,  55,   8,   3,   4,
 	   TILE_SIZE_1x1,
 	   HZ_TEMP | HZ_ZON5 | HZ_ZON4,
 	   CT_PASSENGERS, CT_MAIL, CT_GOODS), // 01
-	MS(1968, MAX_YEAR,  40, 100, STR_TOWN_BUILDING_NAME_SMALL_BLOCK_OF_FLATS_1,    90,  20,   8,   3,   1,
+	MS(1968, CalendarTime::MAX_YEAR,  40, 100, STR_TOWN_BUILDING_NAME_SMALL_BLOCK_OF_FLATS_1,    90,  20,   8,   3,   1,
 	   TILE_SIZE_1x1,
 	   HZ_TEMP | HZ_ZON4 | HZ_ZON3 | HZ_ZON2,
 	   CT_PASSENGERS, CT_MAIL, CT_GOODS), // 02
-	MS(   0, MAX_YEAR,   5,  90, STR_TOWN_BUILDING_NAME_CHURCH_1,                 230,   2,   2,   0,   0,
+	MS(   0, CalendarTime::MAX_YEAR,   5,  90, STR_TOWN_BUILDING_NAME_CHURCH_1,                 230,   2,   2,   0,   0,
 	   BUILDING_IS_CHURCH | TILE_SIZE_1x1,
 	   HZ_TEMP | HZ_ZON4 | HZ_ZON3 | HZ_ZON2 | HZ_ZON1,
 	   CT_PASSENGERS, CT_MAIL, CT_GOODS), // 03
-	MS(1975, MAX_YEAR, 220, 160, STR_TOWN_BUILDING_NAME_LARGE_OFFICE_BLOCK_1,     160,  85,  10,   4,   6,
+	MS(1975, CalendarTime::MAX_YEAR, 220, 160, STR_TOWN_BUILDING_NAME_LARGE_OFFICE_BLOCK_1,     160,  85,  10,   4,   6,
 	   BUILDING_IS_ANIMATED | TILE_SIZE_1x1,
 	   HZ_TEMP | HZ_SUBARTC_BELOW | HZ_SUBTROPIC | HZ_ZON5,
 	   CT_PASSENGERS, CT_MAIL, CT_GOODS), // 04
-	MS(1975, MAX_YEAR, 220, 160, STR_TOWN_BUILDING_NAME_LARGE_OFFICE_BLOCK_1,     160,  85,  10,   4,   6,
+	MS(1975, CalendarTime::MAX_YEAR, 220, 160, STR_TOWN_BUILDING_NAME_LARGE_OFFICE_BLOCK_1,     160,  85,  10,   4,   6,
 	   BUILDING_IS_ANIMATED | TILE_SIZE_1x1,
 	   HZ_SUBARTC_ABOVE  | HZ_ZON5,
 	   CT_PASSENGERS, CT_MAIL, CT_GOODS), // 05
-	MS(   0, MAX_YEAR,  30,  80, STR_TOWN_BUILDING_NAME_TOWN_HOUSES_1,             80,  12,   4,   1,   0,
+	MS(   0, CalendarTime::MAX_YEAR,  30,  80, STR_TOWN_BUILDING_NAME_TOWN_HOUSES_1,             80,  12,   4,   1,   0,
 	   TILE_SIZE_1x1,
 	   HZ_TEMP | HZ_ZON4 | HZ_ZON3 | HZ_ZON2 | HZ_ZON1,
 	   CT_PASSENGERS, CT_MAIL, CT_GOODS), // 06
-	MS(1959, MAX_YEAR, 140, 180, STR_TOWN_BUILDING_NAME_HOTEL_1,                  150,  22,   6,   1,   2,
+	MS(1959, CalendarTime::MAX_YEAR, 140, 180, STR_TOWN_BUILDING_NAME_HOTEL_1,                  150,  22,   6,   1,   2,
 	   TILE_SIZE_1x2,
 	   HZ_TEMP | HZ_ZON5 | HZ_ZON3,
 	   CT_PASSENGERS, CT_MAIL, CT_GOODS), // 07
-	MS(1959, MAX_YEAR,   0, 180, STR_TOWN_BUILDING_NAME_HOTEL_1,                  150,  22,   6,   1,   2,
+	MS(1959, CalendarTime::MAX_YEAR,   0, 180, STR_TOWN_BUILDING_NAME_HOTEL_1,                  150,  22,   6,   1,   2,
 	   TILE_NO_FLAG,
 	   HZ_NOZNS,
 	   CT_PASSENGERS, CT_MAIL, CT_GOODS), // 08
-	MS(1945, MAX_YEAR,   0,  65, STR_TOWN_BUILDING_NAME_STATUE_1,                  40,   0,   2,   0,   0,
+	MS(1945, CalendarTime::MAX_YEAR,   0,  65, STR_TOWN_BUILDING_NAME_STATUE_1,                  40,   0,   2,   0,   0,
 	   TILE_SIZE_1x1,
 	   HZ_TEMP | HZ_SUBARTC_BELOW | HZ_SUBTROPIC | HZ_ZON5 | HZ_ZON4,
 	   CT_PASSENGERS, CT_MAIL, CT_GOODS), // 09
-	MS(1945, MAX_YEAR,   0,  65, STR_TOWN_BUILDING_NAME_FOUNTAIN_1,                40,   0,   2,   0,   0,
+	MS(1945, CalendarTime::MAX_YEAR,   0,  65, STR_TOWN_BUILDING_NAME_FOUNTAIN_1,                40,   0,   2,   0,   0,
 	   TILE_SIZE_1x1,
 	   HZ_TEMP | HZ_SUBARTC_BELOW | HZ_SUBTROPIC | HZ_ZON5,
 	   CT_PASSENGERS, CT_MAIL, CT_GOODS), // 0A
-	MS(   0, MAX_YEAR,   0,  60, STR_TOWN_BUILDING_NAME_PARK_1,                    75,   0,   2,   0,   0,
+	MS(   0, CalendarTime::MAX_YEAR,   0,  60, STR_TOWN_BUILDING_NAME_PARK_1,                    75,   0,   2,   0,   0,
 	   TILE_SIZE_1x1,
 	   HZ_TEMP | HZ_ZON3,
 	   CT_PASSENGERS, CT_MAIL, CT_GOODS), // 0B
-	MS(1935, MAX_YEAR,   0,  60, STR_TOWN_BUILDING_NAME_PARK_1,                    75,   0,   2,   0,   0,
+	MS(1935, CalendarTime::MAX_YEAR,   0,  60, STR_TOWN_BUILDING_NAME_PARK_1,                    75,   0,   2,   0,   0,
 	   TILE_SIZE_1x1,
 	   HZ_TEMP | HZ_ZON4,
 	   CT_PASSENGERS, CT_MAIL, CT_GOODS), // 0C
-	MS(1951, MAX_YEAR, 150, 130, STR_TOWN_BUILDING_NAME_OFFICE_BLOCK_2,           110,  65,   8,   2,   4,
+	MS(1951, CalendarTime::MAX_YEAR, 150, 130, STR_TOWN_BUILDING_NAME_OFFICE_BLOCK_2,           110,  65,   8,   2,   4,
 	   TILE_SIZE_1x1,
 	   HZ_TEMP | HZ_ZON5 | HZ_ZON4,
 	   CT_PASSENGERS, CT_MAIL, CT_GOODS), // 0D
@@ -1900,31 +1900,31 @@ static const HouseSpec _original_house_s
 	   TILE_SIZE_1x1,
 	   HZ_TEMP | HZ_ZON5 | HZ_ZON4 | HZ_ZON3,
 	   CT_PASSENGERS, CT_MAIL, CT_GOODS), // 10
-	MS(1977, MAX_YEAR, 130, 200, STR_TOWN_BUILDING_NAME_MODERN_OFFICE_BUILDING_1, 150,  50,  10,   3,   6,
+	MS(1977, CalendarTime::MAX_YEAR, 130, 200, STR_TOWN_BUILDING_NAME_MODERN_OFFICE_BUILDING_1, 150,  50,  10,   3,   6,
 	   TILE_SIZE_1x1,
 	   HZ_TEMP | HZ_SUBARTC_BELOW | HZ_SUBTROPIC | HZ_ZON5,
 	   CT_PASSENGERS, CT_MAIL, CT_GOODS), // 11
-	MS(1983, MAX_YEAR,   6, 145, STR_TOWN_BUILDING_NAME_WAREHOUSE_1,              110,  10,   6,   3,   8,
+	MS(1983, CalendarTime::MAX_YEAR,   6, 145, STR_TOWN_BUILDING_NAME_WAREHOUSE_1,              110,  10,   6,   3,   8,
 	   TILE_SIZE_1x1,
 	   HZ_TEMP | HZ_ZON5,
 	   CT_PASSENGERS, CT_MAIL, CT_GOODS), // 12
-	MS(1985, MAX_YEAR, 110, 155, STR_TOWN_BUILDING_NAME_OFFICE_BLOCK_3,           110,  55,   6,   2,   6,
+	MS(1985, CalendarTime::MAX_YEAR, 110, 155, STR_TOWN_BUILDING_NAME_OFFICE_BLOCK_3,           110,  55,   6,   2,   6,
 	   TILE_SIZE_1x1,
 	   HZ_TEMP | HZ_ZON5,
 	   CT_PASSENGERS, CT_MAIL, CT_GOODS), // 13
-	MS(   0, MAX_YEAR,  65, 250, STR_TOWN_BUILDING_NAME_STADIUM_1,                300,   5,   4,   0,   0,
+	MS(   0, CalendarTime::MAX_YEAR,  65, 250, STR_TOWN_BUILDING_NAME_STADIUM_1,                300,   5,   4,   0,   0,
 	   BUILDING_IS_STADIUM | TILE_SIZE_2x2,
 	   HZ_TEMP | HZ_ZON4 | HZ_ZON3 | HZ_ZON2 | HZ_ZON1,
 	   CT_PASSENGERS, CT_MAIL, CT_GOODS), // 14
-	MS(   0, MAX_YEAR,   0, 250, STR_TOWN_BUILDING_NAME_STADIUM_1,                300,   5,   4,   0,   0,
+	MS(   0, CalendarTime::MAX_YEAR,   0, 250, STR_TOWN_BUILDING_NAME_STADIUM_1,                300,   5,   4,   0,   0,
 	   TILE_NO_FLAG,
 	   HZ_NOZNS,
 	   CT_PASSENGERS, CT_MAIL, CT_GOODS), // 15
-	MS(   0, MAX_YEAR,   0, 250, STR_TOWN_BUILDING_NAME_STADIUM_1,                300,   5,   4,   0,   0,
+	MS(   0, CalendarTime::MAX_YEAR,   0, 250, STR_TOWN_BUILDING_NAME_STADIUM_1,                300,   5,   4,   0,   0,
 	   TILE_NO_FLAG,
 	   HZ_NOZNS,
 	   CT_PASSENGERS, CT_MAIL, CT_GOODS), // 16
-	MS(   0, MAX_YEAR,   0, 250, STR_TOWN_BUILDING_NAME_STADIUM_1,                300,   5,   4,   0,   0,
+	MS(   0, CalendarTime::MAX_YEAR,   0, 250, STR_TOWN_BUILDING_NAME_STADIUM_1,                300,   5,   4,   0,   0,
 	   TILE_NO_FLAG,
 	   HZ_NOZNS,
 	   CT_PASSENGERS, CT_MAIL, CT_GOODS), // 17
@@ -1936,15 +1936,15 @@ static const HouseSpec _original_house_s
 	   TILE_SIZE_1x1,
 	   HZ_TEMP | HZ_ZON1,
 	   CT_PASSENGERS, CT_MAIL, CT_GOODS), // 19
-	MS(1931, MAX_YEAR,  13,  71, STR_TOWN_BUILDING_NAME_HOUSES_1,                  75,   8,   3,   1,   0,
+	MS(1931, CalendarTime::MAX_YEAR,  13,  71, STR_TOWN_BUILDING_NAME_HOUSES_1,                  75,   8,   3,   1,   0,
 	   TILE_SIZE_1x1,
 	   HZ_TEMP | HZ_ZON4 | HZ_ZON3 | HZ_ZON2 | HZ_ZON1,
 	   CT_PASSENGERS, CT_MAIL, CT_GOODS), // 1A
-	MS(1935, MAX_YEAR, 100, 135, STR_TOWN_BUILDING_NAME_FLATS_1,                  100,  35,   7,   2,   2,
+	MS(1935, CalendarTime::MAX_YEAR, 100, 135, STR_TOWN_BUILDING_NAME_FLATS_1,                  100,  35,   7,   2,   2,
 	   TILE_SIZE_1x1,
 	   HZ_TEMP | HZ_ZON5 | HZ_ZON4 | HZ_ZON3,
 	   CT_PASSENGERS, CT_MAIL, CT_GOODS), // 1B
-	MS(1963, MAX_YEAR, 170, 145, STR_TOWN_BUILDING_NAME_TALL_OFFICE_BLOCK_2,      170,  50,   8,   3,   3,
+	MS(1963, CalendarTime::MAX_YEAR, 170, 145, STR_TOWN_BUILDING_NAME_TALL_OFFICE_BLOCK_2,      170,  50,   8,   3,   3,
 	   TILE_SIZE_1x1,
 	   HZ_TEMP | HZ_ZON5 | HZ_ZON4 | HZ_ZON3,
 	   CT_PASSENGERS, CT_MAIL, CT_GOODS), // 1C
@@ -1952,31 +1952,31 @@ static const HouseSpec _original_house_s
 	   TILE_SIZE_1x1,
 	   HZ_TEMP | HZ_ZON5 | HZ_ZON4 | HZ_ZON3,
 	   CT_PASSENGERS, CT_MAIL, CT_GOODS), // 1D
-	MS(1973, MAX_YEAR, 180, 155, STR_TOWN_BUILDING_NAME_SHOPS_AND_OFFICES_3,      180,  64,   8,   3,   3,
+	MS(1973, CalendarTime::MAX_YEAR, 180, 155, STR_TOWN_BUILDING_NAME_SHOPS_AND_OFFICES_3,      180,  64,   8,   3,   3,
 	   TILE_SIZE_1x1,
 	   HZ_TEMP | HZ_SUBTROPIC | HZ_ZON5 | HZ_ZON3,
 	   CT_PASSENGERS, CT_MAIL, CT_GOODS), // 1E
-	MS(   0, MAX_YEAR,  35, 220, STR_TOWN_BUILDING_NAME_THEATER_1,                230,  23,   8,   2,   2,
+	MS(   0, CalendarTime::MAX_YEAR,  35, 220, STR_TOWN_BUILDING_NAME_THEATER_1,                230,  23,   8,   2,   2,
 	   TILE_SIZE_1x1,
 	   HZ_TEMP | HZ_ZON5 | HZ_ZON4,
 	   CT_PASSENGERS, CT_MAIL, CT_GOODS), // 1F
-	MS(1958, MAX_YEAR,  65, 250, STR_TOWN_BUILDING_NAME_STADIUM_2,                300,   5,   4,   0,   0,
+	MS(1958, CalendarTime::MAX_YEAR,  65, 250, STR_TOWN_BUILDING_NAME_STADIUM_2,                300,   5,   4,   0,   0,
 	   BUILDING_IS_STADIUM | TILE_SIZE_2x2,
 	   HZ_TEMP | HZ_SUBARTC_BELOW | HZ_SUBTROPIC | HZ_ZON4 | HZ_ZON3 | HZ_ZON2 | HZ_ZON1,
 	   CT_PASSENGERS, CT_MAIL, CT_GOODS), // 20
-	MS(1958, MAX_YEAR,   0, 250, STR_TOWN_BUILDING_NAME_STADIUM_2,                300,   5,   4,   0,   0,
+	MS(1958, CalendarTime::MAX_YEAR,   0, 250, STR_TOWN_BUILDING_NAME_STADIUM_2,                300,   5,   4,   0,   0,
 	   TILE_NO_FLAG,
 	   HZ_NOZNS,
 	   CT_PASSENGERS, CT_MAIL, CT_GOODS), // 21
-	MS(1958, MAX_YEAR,   0, 250, STR_TOWN_BUILDING_NAME_STADIUM_2,                300,   5,   4,   0,   0,
+	MS(1958, CalendarTime::MAX_YEAR,   0, 250, STR_TOWN_BUILDING_NAME_STADIUM_2,                300,   5,   4,   0,   0,
 	   TILE_NO_FLAG,
 	   HZ_NOZNS,
 	   CT_PASSENGERS, CT_MAIL, CT_GOODS), // 22
-	MS(1958, MAX_YEAR,   0, 250, STR_TOWN_BUILDING_NAME_STADIUM_2,                300,   5,   4,   0,   0,
+	MS(1958, CalendarTime::MAX_YEAR,   0, 250, STR_TOWN_BUILDING_NAME_STADIUM_2,                300,   5,   4,   0,   0,
 	   TILE_NO_FLAG,
 	   HZ_NOZNS,
 	   CT_PASSENGERS, CT_MAIL, CT_GOODS), // 23
-	MS(2000, MAX_YEAR, 140, 170, STR_TOWN_BUILDING_NAME_OFFICES_1,                250,  65,   8,   3,   2,
+	MS(2000, CalendarTime::MAX_YEAR, 140, 170, STR_TOWN_BUILDING_NAME_OFFICES_1,                250,  65,   8,   3,   2,
 	   TILE_SIZE_1x1,
 	   HZ_TEMP | HZ_SUBARTC_BELOW | HZ_SUBTROPIC | HZ_ZON5 | HZ_ZON4,
 	   CT_PASSENGERS, CT_MAIL, CT_GOODS), // 24
@@ -1988,39 +1988,39 @@ static const HouseSpec _original_house_s
 	   TILE_SIZE_1x1,
 	   HZ_SUBARTC_ABOVE | HZ_ZON2 | HZ_ZON1,
 	   CT_PASSENGERS, CT_MAIL, CT_FOOD), // 26
-	MS(1945, MAX_YEAR,  35, 210, STR_TOWN_BUILDING_NAME_CINEMA_1,                 230,  23,   8,   2,   2,
+	MS(1945, CalendarTime::MAX_YEAR,  35, 210, STR_TOWN_BUILDING_NAME_CINEMA_1,                 230,  23,   8,   2,   2,
 	   TILE_SIZE_1x1,
 	   HZ_TEMP | HZ_ZON5 | HZ_ZON4 | HZ_ZON3,
 	   CT_PASSENGERS, CT_MAIL, CT_GOODS), // 27
-	MS(1983, MAX_YEAR, 180, 250, STR_TOWN_BUILDING_NAME_SHOPPING_MALL_1,          300,   5,   8,   2,   3,
+	MS(1983, CalendarTime::MAX_YEAR, 180, 250, STR_TOWN_BUILDING_NAME_SHOPPING_MALL_1,          300,   5,   8,   2,   3,
 	   TILE_SIZE_2x2,
 	   HZ_TEMP | HZ_ZON5 | HZ_ZON4 | HZ_ZON3 |HZ_ZON2,
 	   CT_PASSENGERS, CT_MAIL, CT_GOODS), // 28
-	MS(1983, MAX_YEAR,   0, 250, STR_TOWN_BUILDING_NAME_SHOPPING_MALL_1,          300,   5,   8,   2,   3,
+	MS(1983, CalendarTime::MAX_YEAR,   0, 250, STR_TOWN_BUILDING_NAME_SHOPPING_MALL_1,          300,   5,   8,   2,   3,
 	   TILE_NO_FLAG,
 	   HZ_NOZNS,
 	   CT_PASSENGERS, CT_MAIL, CT_GOODS), // 29
-	MS(1983, MAX_YEAR,   0, 250, STR_TOWN_BUILDING_NAME_SHOPPING_MALL_1,          300,   5,   8,   2,   3,
+	MS(1983, CalendarTime::MAX_YEAR,   0, 250, STR_TOWN_BUILDING_NAME_SHOPPING_MALL_1,          300,   5,   8,   2,   3,
 	   TILE_NO_FLAG,
 	   HZ_NOZNS,
 	   CT_PASSENGERS, CT_MAIL, CT_GOODS), // 2A
-	MS(1983, MAX_YEAR,   0, 250, STR_TOWN_BUILDING_NAME_SHOPPING_MALL_1,          300,   5,   8,   2,   3,
+	MS(1983, CalendarTime::MAX_YEAR,   0, 250, STR_TOWN_BUILDING_NAME_SHOPPING_MALL_1,          300,   5,   8,   2,   3,
 	   TILE_NO_FLAG,
 	   HZ_NOZNS,
 	   CT_PASSENGERS, CT_MAIL, CT_GOODS), // 2B
-	MS(   0, MAX_YEAR,  80, 100, STR_TOWN_BUILDING_NAME_FLATS_1,                   90,  20,   5,   2,   2,
+	MS(   0, CalendarTime::MAX_YEAR,  80, 100, STR_TOWN_BUILDING_NAME_FLATS_1,                   90,  20,   5,   2,   2,
 	   TILE_SIZE_1x1,
 	   HZ_SUBARTC_BELOW | HZ_ZON5 | HZ_ZON4 | HZ_ZON3,
 	   CT_PASSENGERS, CT_MAIL, CT_FOOD), // 2C
-	MS(   0, MAX_YEAR,  80, 100, STR_TOWN_BUILDING_NAME_FLATS_1,                   90,  20,   5,   2,   2,
+	MS(   0, CalendarTime::MAX_YEAR,  80, 100, STR_TOWN_BUILDING_NAME_FLATS_1,                   90,  20,   5,   2,   2,
 	   TILE_SIZE_1x1,
 	   HZ_SUBARTC_ABOVE  | HZ_ZON5 | HZ_ZON4 | HZ_ZON3,
 	   CT_PASSENGERS, CT_MAIL, CT_FOOD), // 2D
-	MS(   0, MAX_YEAR,  16,  70, STR_TOWN_BUILDING_NAME_HOUSES_2,                  70,   6,   3,   1,   2,
+	MS(   0, CalendarTime::MAX_YEAR,  16,  70, STR_TOWN_BUILDING_NAME_HOUSES_2,                  70,   6,   3,   1,   2,
 	   TILE_SIZE_1x1,
 	   HZ_SUBARTC_BELOW | HZ_ZON4 | HZ_ZON3 | HZ_ZON2 | HZ_ZON1,
 	   CT_PASSENGERS, CT_MAIL, CT_FOOD), // 2E
-	MS(   0, MAX_YEAR,  16,  70, STR_TOWN_BUILDING_NAME_HOUSES_2,                  70,   6,   3,   1,   2,
+	MS(   0, CalendarTime::MAX_YEAR,  16,  70, STR_TOWN_BUILDING_NAME_HOUSES_2,                  70,   6,   3,   1,   2,
 	   TILE_SIZE_1x1,
 	   HZ_SUBARTC_ABOVE | HZ_ZON4 | HZ_ZON3 | HZ_ZON2 | HZ_ZON1,
 	   CT_PASSENGERS, CT_MAIL, CT_FOOD), // 2F
@@ -2032,59 +2032,59 @@ static const HouseSpec _original_house_s
 	   TILE_SIZE_1x1,
 	   HZ_SUBARTC_ABOVE | HZ_ZON3 | HZ_ZON2 | HZ_ZON1,
 	   CT_PASSENGERS, CT_MAIL, CT_FOOD), // 31
-	MS(1966, MAX_YEAR, 135, 150, STR_TOWN_BUILDING_NAME_TALL_OFFICE_BLOCK_1,      120,  60,   8,   3,   4,
+	MS(1966, CalendarTime::MAX_YEAR, 135, 150, STR_TOWN_BUILDING_NAME_TALL_OFFICE_BLOCK_1,      120,  60,   8,   3,   4,
 	   TILE_SIZE_1x1,
 	   HZ_SUBARTC_BELOW | HZ_SUBTROPIC | HZ_ZON5 | HZ_ZON4,
 	   CT_PASSENGERS, CT_MAIL, CT_GOODS), // 32
-	MS(1966, MAX_YEAR, 135, 150, STR_TOWN_BUILDING_NAME_TALL_OFFICE_BLOCK_1,      120,  60,   8,   3,   4,
+	MS(1966, CalendarTime::MAX_YEAR, 135, 150, STR_TOWN_BUILDING_NAME_TALL_OFFICE_BLOCK_1,      120,  60,   8,   3,   4,
 	   TILE_SIZE_1x1,
 	   HZ_SUBARTC_ABOVE | HZ_ZON5 | HZ_ZON4,
 	   CT_PASSENGERS, CT_MAIL, CT_GOODS), // 33
-	MS(1970, MAX_YEAR, 170, 170, STR_TOWN_BUILDING_NAME_TALL_OFFICE_BLOCK_1,      130,  70,   9,   3,   4,
+	MS(1970, CalendarTime::MAX_YEAR, 170, 170, STR_TOWN_BUILDING_NAME_TALL_OFFICE_BLOCK_1,      130,  70,   9,   3,   4,
 	   TILE_SIZE_1x1,
 	   HZ_SUBARTC_BELOW | HZ_ZON5 | HZ_ZON4,
 	   CT_PASSENGERS, CT_MAIL, CT_GOODS), // 34
-	MS(1970, MAX_YEAR, 170, 170, STR_TOWN_BUILDING_NAME_TALL_OFFICE_BLOCK_1,      130,  70,   9,   3,   4,
+	MS(1970, CalendarTime::MAX_YEAR, 170, 170, STR_TOWN_BUILDING_NAME_TALL_OFFICE_BLOCK_1,      130,  70,   9,   3,   4,
 	   TILE_SIZE_1x1,
 	   HZ_SUBARTC_ABOVE | HZ_ZON5 | HZ_ZON4,
 	   CT_PASSENGERS, CT_MAIL, CT_GOODS), // 35
-	MS(1974, MAX_YEAR, 210, 200, STR_TOWN_BUILDING_NAME_TALL_OFFICE_BLOCK_1,      140,  80,  10,   3,   5,
+	MS(1974, CalendarTime::MAX_YEAR, 210, 200, STR_TOWN_BUILDING_NAME_TALL_OFFICE_BLOCK_1,      140,  80,  10,   3,   5,
 	   TILE_SIZE_1x1,
 	   HZ_SUBARTC_BELOW | HZ_SUBTROPIC | HZ_ZON5 | HZ_ZON4,
 	   CT_PASSENGERS, CT_MAIL, CT_GOODS), // 36
-	MS(1974, MAX_YEAR, 210, 200, STR_TOWN_BUILDING_NAME_TALL_OFFICE_BLOCK_1,      140,  80,  10,   3,   5,
+	MS(1974, CalendarTime::MAX_YEAR, 210, 200, STR_TOWN_BUILDING_NAME_TALL_OFFICE_BLOCK_1,      140,  80,  10,   3,   5,
 	   TILE_SIZE_1x1,
 	   HZ_SUBARTC_ABOVE | HZ_ZON5 | HZ_ZON4,
 	   CT_PASSENGERS, CT_MAIL, CT_GOODS), // 37
-	MS(   0, MAX_YEAR,  10,  60, STR_TOWN_BUILDING_NAME_HOUSES_2,                  60,   5,   2,   1,   1,
+	MS(   0, CalendarTime::MAX_YEAR,  10,  60, STR_TOWN_BUILDING_NAME_HOUSES_2,                  60,   5,   2,   1,   1,
 	   TILE_SIZE_1x1,
 	   HZ_SUBARTC_BELOW | HZ_ZON1,
 	   CT_PASSENGERS, CT_MAIL, CT_FOOD), // 38
-	MS(   0, MAX_YEAR,  10,  60, STR_TOWN_BUILDING_NAME_HOUSES_2,                  60,   5,   2,   1,   1,
+	MS(   0, CalendarTime::MAX_YEAR,  10,  60, STR_TOWN_BUILDING_NAME_HOUSES_2,                  60,   5,   2,   1,   1,
 	   TILE_SIZE_1x1,
 	   HZ_SUBARTC_ABOVE | HZ_ZON1,
 	   CT_PASSENGERS, CT_MAIL, CT_FOOD), // 39
-	MS(   0, MAX_YEAR,  25, 100, STR_TOWN_BUILDING_NAME_SHOPS_AND_OFFICES_1,       80,  20,   3,   1,   1,
+	MS(   0, CalendarTime::MAX_YEAR,  25, 100, STR_TOWN_BUILDING_NAME_SHOPS_AND_OFFICES_1,       80,  20,   3,   1,   1,
 	   TILE_SIZE_1x1,
 	   HZ_SUBARTC_BELOW | HZ_ZON5 | HZ_ZON4 | HZ_ZON3 | HZ_ZON2,
 	   CT_PASSENGERS, CT_MAIL, CT_FOOD), // 3A
-	MS(   0, MAX_YEAR,  25, 100, STR_TOWN_BUILDING_NAME_SHOPS_AND_OFFICES_1,       80,  20,   3,   1,   1,
+	MS(   0, CalendarTime::MAX_YEAR,  25, 100, STR_TOWN_BUILDING_NAME_SHOPS_AND_OFFICES_1,       80,  20,   3,   1,   1,
 	   TILE_SIZE_1x1,
 	   HZ_SUBARTC_ABOVE | HZ_ZON5 | HZ_ZON4 | HZ_ZON3 | HZ_ZON2,
 	   CT_PASSENGERS, CT_MAIL, CT_FOOD), // 3B
-	MS(   0, MAX_YEAR,   6,  85, STR_TOWN_BUILDING_NAME_CHURCH_1,                 230,   2,   2,   0,   0,
+	MS(   0, CalendarTime::MAX_YEAR,   6,  85, STR_TOWN_BUILDING_NAME_CHURCH_1,                 230,   2,   2,   0,   0,
 	   BUILDING_IS_CHURCH | TILE_SIZE_1x1,
 	   HZ_SUBARTC_BELOW | HZ_ZON4 | HZ_ZON3 | HZ_ZON2 | HZ_ZON1,
 	   CT_PASSENGERS, CT_MAIL, CT_GOODS), // 3C
-	MS(   0, MAX_YEAR,   6,  85, STR_TOWN_BUILDING_NAME_CHURCH_1,                 230,   2,   2,   0,   0,
+	MS(   0, CalendarTime::MAX_YEAR,   6,  85, STR_TOWN_BUILDING_NAME_CHURCH_1,                 230,   2,   2,   0,   0,
 	   BUILDING_IS_CHURCH | TILE_SIZE_1x1,
 	   HZ_SUBARTC_ABOVE | HZ_ZON4 | HZ_ZON3 | HZ_ZON2 | HZ_ZON1,
 	   CT_PASSENGERS, CT_MAIL, CT_GOODS), // 3D
-	MS(   0, MAX_YEAR,  17,  80, STR_TOWN_BUILDING_NAME_HOUSES_2,                  80,   7,   3,   1,   1,
+	MS(   0, CalendarTime::MAX_YEAR,  17,  80, STR_TOWN_BUILDING_NAME_HOUSES_2,                  80,   7,   3,   1,   1,
 	   TILE_SIZE_1x1,
 	   HZ_SUBARTC_BELOW | HZ_ZON3 | HZ_ZON2 | HZ_ZON1,
 	   CT_PASSENGERS, CT_MAIL, CT_FOOD), // 3E
-	MS(   0, MAX_YEAR,  17,  80, STR_TOWN_BUILDING_NAME_HOUSES_2,                  80,   7,   3,   1,   1,
+	MS(   0, CalendarTime::MAX_YEAR,  17,  80, STR_TOWN_BUILDING_NAME_HOUSES_2,                  80,   7,   3,   1,   1,
 	   TILE_SIZE_1x1,
 	   HZ_SUBARTC_ABOVE | HZ_ZON3 | HZ_ZON2 | HZ_ZON1,
 	   CT_PASSENGERS, CT_MAIL, CT_FOOD), // 3F
@@ -2096,179 +2096,179 @@ static const HouseSpec _original_house_s
 	   TILE_SIZE_1x1,
 	   HZ_SUBARTC_ABOVE| HZ_ZON5 | HZ_ZON4 | HZ_ZON3,
 	   CT_PASSENGERS, CT_MAIL, CT_GOODS), // 41
-	MS(1972, MAX_YEAR, 140, 160, STR_TOWN_BUILDING_NAME_HOTEL_1,                  160,  25,   6,   1,   3,
+	MS(1972, CalendarTime::MAX_YEAR, 140, 160, STR_TOWN_BUILDING_NAME_HOTEL_1,                  160,  25,   6,   1,   3,
 	   TILE_SIZE_1x2,
 	   HZ_SUBARTC_BELOW| HZ_ZON5 | HZ_ZON4 | HZ_ZON3,
 	   CT_PASSENGERS, CT_MAIL, CT_FOOD), // 42
-	MS(1972, MAX_YEAR,   0, 160, STR_TOWN_BUILDING_NAME_HOTEL_1,                  160,  25,   6,   1,   2,
+	MS(1972, CalendarTime::MAX_YEAR,   0, 160, STR_TOWN_BUILDING_NAME_HOTEL_1,                  160,  25,   6,   1,   2,
 	   TILE_NO_FLAG,
 	   HZ_NOZNS,
 	   CT_PASSENGERS, CT_MAIL, CT_GOODS), // 43
-	MS(1972, MAX_YEAR, 140, 160, STR_TOWN_BUILDING_NAME_HOTEL_1,                  160,  25,   6,   1,   3,
+	MS(1972, CalendarTime::MAX_YEAR, 140, 160, STR_TOWN_BUILDING_NAME_HOTEL_1,                  160,  25,   6,   1,   3,
 	   TILE_SIZE_1x2,
 	   HZ_SUBARTC_ABOVE| HZ_ZON5 | HZ_ZON4 | HZ_ZON3,
 	   CT_PASSENGERS, CT_MAIL, CT_FOOD), // 44
-	MS(1972, MAX_YEAR,   0, 160, STR_TOWN_BUILDING_NAME_HOTEL_1,                  160,  25,   6,   1,   2,
+	MS(1972, CalendarTime::MAX_YEAR,   0, 160, STR_TOWN_BUILDING_NAME_HOTEL_1,                  160,  25,   6,   1,   2,
 	   TILE_NO_FLAG,
 	   HZ_NOZNS,
 	   CT_PASSENGERS, CT_MAIL, CT_GOODS), // 45
-	MS(1963, MAX_YEAR, 105, 130, STR_TOWN_BUILDING_NAME_SHOPS_AND_OFFICES_1,      105,  50,   7,   2,   3,
+	MS(1963, CalendarTime::MAX_YEAR, 105, 130, STR_TOWN_BUILDING_NAME_SHOPS_AND_OFFICES_1,      105,  50,   7,   2,   3,
 	   TILE_SIZE_1x1,
 	   HZ_SUBARTC_BELOW | HZ_SUBTROPIC | HZ_ZON5 | HZ_ZON4 | HZ_ZON3,
 	   CT_PASSENGERS, CT_MAIL, CT_GOODS), // 46
-	MS(1963, MAX_YEAR, 105, 130, STR_TOWN_BUILDING_NAME_SHOPS_AND_OFFICES_1,      105,  50,   7,   2,   3,
+	MS(1963, CalendarTime::MAX_YEAR, 105, 130, STR_TOWN_BUILDING_NAME_SHOPS_AND_OFFICES_1,      105,  50,   7,   2,   3,
 	   TILE_SIZE_1x1,
 	   HZ_SUBARTC_ABOVE| HZ_ZON5 | HZ_ZON4 | HZ_ZON3,
 	   CT_PASSENGERS, CT_MAIL, CT_GOODS), // 47
-	MS(1978, MAX_YEAR, 190, 190, STR_TOWN_BUILDING_NAME_TALL_OFFICE_BLOCK_1,      135,  75,   9,   3,   4,
+	MS(1978, CalendarTime::MAX_YEAR, 190, 190, STR_TOWN_BUILDING_NAME_TALL_OFFICE_BLOCK_1,      135,  75,   9,   3,   4,
 	   TILE_SIZE_1x1,
 	   HZ_SUBARTC_BELOW | HZ_ZON5 | HZ_ZON4,
 	   CT_PASSENGERS, CT_MAIL, CT_GOODS), // 48
-	MS(1978, MAX_YEAR, 190, 190, STR_TOWN_BUILDING_NAME_TALL_OFFICE_BLOCK_1,      135,  75,   9,   3,   4,
+	MS(1978, CalendarTime::MAX_YEAR, 190, 190, STR_TOWN_BUILDING_NAME_TALL_OFFICE_BLOCK_1,      135,  75,   9,   3,   4,
 	   TILE_SIZE_1x1,
 	   HZ_SUBARTC_ABOVE | HZ_ZON5 | HZ_ZON4,
 	   CT_PASSENGERS, CT_MAIL, CT_GOODS), // 49
-	MS(1967, MAX_YEAR, 250, 140, STR_TOWN_BUILDING_NAME_TALL_OFFICE_BLOCK_1,      200,  60,   7,   2,   2,
+	MS(1967, CalendarTime::MAX_YEAR, 250, 140, STR_TOWN_BUILDING_NAME_TALL_OFFICE_BLOCK_1,      200,  60,   7,   2,   2,
 	   TILE_SIZE_2x1,
 	   HZ_SUBARTC_BELOW| HZ_ZON5 | HZ_ZON4 | HZ_ZON3,
 	   CT_PASSENGERS, CT_MAIL, CT_GOODS), // 4A
-	MS(1967, MAX_YEAR,   0, 140, STR_TOWN_BUILDING_NAME_TALL_OFFICE_BLOCK_1,      200,  60,   7,   2,   2,
+	MS(1967, CalendarTime::MAX_YEAR,   0, 140, STR_TOWN_BUILDING_NAME_TALL_OFFICE_BLOCK_1,      200,  60,   7,   2,   2,
 	   TILE_NO_FLAG,
 	   HZ_NOZNS,
 	   CT_PASSENGERS, CT_MAIL, CT_GOODS), // 4B
-	MS(1967, MAX_YEAR, 250, 140, STR_TOWN_BUILDING_NAME_TALL_OFFICE_BLOCK_1,      200,  60,   7,   2,   2,
+	MS(1967, CalendarTime::MAX_YEAR, 250, 140, STR_TOWN_BUILDING_NAME_TALL_OFFICE_BLOCK_1,      200,  60,   7,   2,   2,
 	   TILE_SIZE_2x1,
 	   HZ_SUBARTC_ABOVE | HZ_ZON5 | HZ_ZON4 | HZ_ZON3,
 	   CT_PASSENGERS, CT_MAIL, CT_GOODS), // 4C
-	MS(1967, MAX_YEAR,   0, 140, STR_TOWN_BUILDING_NAME_TALL_OFFICE_BLOCK_1,      200,  60,   7,   2,   2,
+	MS(1967, CalendarTime::MAX_YEAR,   0, 140, STR_TOWN_BUILDING_NAME_TALL_OFFICE_BLOCK_1,      200,  60,   7,   2,   2,
 	   TILE_NO_FLAG,
 	   HZ_NOZNS,
 	   CT_PASSENGERS, CT_MAIL, CT_GOODS), // 4D
-	MS(   0, MAX_YEAR,  16,  80, STR_TOWN_BUILDING_NAME_HOUSES_2,                  80,   6,   3,   1,   2,
+	MS(   0, CalendarTime::MAX_YEAR,  16,  80, STR_TOWN_BUILDING_NAME_HOUSES_2,                  80,   6,   3,   1,   2,
 	   TILE_SIZE_1x1,
 	   HZ_SUBTROPIC | HZ_ZON5 | HZ_ZON4 | HZ_ZON3 | HZ_ZON2,
 	   CT_PASSENGERS, CT_MAIL, CT_FOOD), // 4E
-	MS(   0, MAX_YEAR,  16,  80, STR_TOWN_BUILDING_NAME_HOUSES_2,                  80,   6,   3,   1,   2,
+	MS(   0, CalendarTime::MAX_YEAR,  16,  80, STR_TOWN_BUILDING_NAME_HOUSES_2,                  80,   6,   3,   1,   2,
 	   TILE_SIZE_1x1,
 	   HZ_SUBTROPIC | HZ_ZON5 | HZ_ZON4 | HZ_ZON3 | HZ_ZON2,
 	   CT_PASSENGERS, CT_MAIL, CT_FOOD), // 4F
-	MS(   0, MAX_YEAR,  16,  80, STR_TOWN_BUILDING_NAME_HOUSES_2,                  80,   5,   3,   1,   2,
+	MS(   0, CalendarTime::MAX_YEAR,  16,  80, STR_TOWN_BUILDING_NAME_HOUSES_2,                  80,   5,   3,   1,   2,
 	   TILE_SIZE_1x1,
 	   HZ_SUBTROPIC | HZ_ZON5 | HZ_ZON4 | HZ_ZON3 | HZ_ZON2,
 	   CT_PASSENGERS, CT_MAIL, CT_FOOD), // 50
-	MS(   0, MAX_YEAR,   7,  30, STR_TOWN_BUILDING_NAME_HOUSES_2,                  30,   4,   3,   1,   1,
+	MS(   0, CalendarTime::MAX_YEAR,   7,  30, STR_TOWN_BUILDING_NAME_HOUSES_2,                  30,   4,   3,   1,   1,
 	   TILE_SIZE_1x1,
 	   HZ_SUBTROPIC | HZ_ZON1,
 	   CT_PASSENGERS, CT_MAIL, CT_FOOD), // 51
-	MS(   0, MAX_YEAR,  45, 130, STR_TOWN_BUILDING_NAME_FLATS_1,                   95,  15,   6,   2,   1,
+	MS(   0, CalendarTime::MAX_YEAR,  45, 130, STR_TOWN_BUILDING_NAME_FLATS_1,                   95,  15,   6,   2,   1,
 	   TILE_SIZE_1x1,
 	   HZ_SUBTROPIC | HZ_ZON5 | HZ_ZON4 | HZ_ZON3,
 	   CT_PASSENGERS, CT_MAIL, CT_GOODS), // 52
-	MS(   0, MAX_YEAR,   8,  90, STR_TOWN_BUILDING_NAME_CHURCH_1,                 200,   3,   2,   0,   0,
+	MS(   0, CalendarTime::MAX_YEAR,   8,  90, STR_TOWN_BUILDING_NAME_CHURCH_1,                 200,   3,   2,   0,   0,
 	   BUILDING_IS_CHURCH | TILE_SIZE_1x1,
 	   HZ_SUBTROPIC | HZ_ZON4 | HZ_ZON3 | HZ_ZON2,
 	   CT_PASSENGERS, CT_MAIL, CT_GOODS), // 53
-	MS(   0, MAX_YEAR,  18,  80, STR_TOWN_BUILDING_NAME_HOUSES_2,                  80,   7,   3,   1,   2,
+	MS(   0, CalendarTime::MAX_YEAR,  18,  80, STR_TOWN_BUILDING_NAME_HOUSES_2,                  80,   7,   3,   1,   2,
 	   TILE_SIZE_1x1,
 	   HZ_SUBTROPIC | HZ_ZON5 | HZ_ZON4 | HZ_ZON3 | HZ_ZON2,
 	   CT_PASSENGERS, CT_MAIL, CT_FOOD), // 54
-	MS(1973, MAX_YEAR,  90, 110, STR_TOWN_BUILDING_NAME_FLATS_1,                   95,  24,   6,   2,   1,
+	MS(1973, CalendarTime::MAX_YEAR,  90, 110, STR_TOWN_BUILDING_NAME_FLATS_1,                   95,  24,   6,   2,   1,
 	   TILE_SIZE_1x1,
 	   HZ_SUBTROPIC | HZ_ZON5 | HZ_ZON4 | HZ_ZON3,
 	   CT_PASSENGERS, CT_MAIL, CT_GOODS), // 55
-	MS(1962, MAX_YEAR, 120, 120, STR_TOWN_BUILDING_NAME_FLATS_1,                   95,  25,   6,   2,   1,
+	MS(1962, CalendarTime::MAX_YEAR, 120, 120, STR_TOWN_BUILDING_NAME_FLATS_1,                   95,  25,   6,   2,   1,
 	   TILE_SIZE_1x1,
 	   HZ_SUBTROPIC | HZ_ZON5 | HZ_ZON4 | HZ_ZON3,
 	   CT_PASSENGERS, CT_MAIL, CT_GOODS), // 56
-	MS(1984, MAX_YEAR, 250, 190, STR_TOWN_BUILDING_NAME_TALL_OFFICE_BLOCK_1,      140,  80,   8,   3,   4,
+	MS(1984, CalendarTime::MAX_YEAR, 250, 190, STR_TOWN_BUILDING_NAME_TALL_OFFICE_BLOCK_1,      140,  80,   8,   3,   4,
 	   TILE_SIZE_2x1,
 	   HZ_SUBTROPIC | HZ_ZON5 | HZ_ZON4,
 	   CT_PASSENGERS, CT_MAIL, CT_GOODS), // 57
-	MS(1984, MAX_YEAR,   0, 190, STR_TOWN_BUILDING_NAME_TALL_OFFICE_BLOCK_1,      140,  80,   8,   3,   4,
+	MS(1984, CalendarTime::MAX_YEAR,   0, 190, STR_TOWN_BUILDING_NAME_TALL_OFFICE_BLOCK_1,      140,  80,   8,   3,   4,
 	   TILE_NO_FLAG,
 	   HZ_SUBTROPIC,
 	   CT_PASSENGERS, CT_MAIL, CT_GOODS), // 58
-	MS(   0, MAX_YEAR,  80, 110, STR_TOWN_BUILDING_NAME_FLATS_1,                   95,  23,   6,   2,   1,
+	MS(   0, CalendarTime::MAX_YEAR,  80, 110, STR_TOWN_BUILDING_NAME_FLATS_1,                   95,  23,   6,   2,   1,
 	   TILE_SIZE_1x1,
 	   HZ_SUBTROPIC | HZ_ZON5 | HZ_ZON4 | HZ_ZON3,
 	   CT_PASSENGERS, CT_MAIL, CT_GOODS), // 59
-	MS(1993, MAX_YEAR, 180, 180, STR_TOWN_BUILDING_NAME_TALL_OFFICE_BLOCK_1,      150,  90,   8,   3,   4,
+	MS(1993, CalendarTime::MAX_YEAR, 180, 180, STR_TOWN_BUILDING_NAME_TALL_OFFICE_BLOCK_1,      150,  90,   8,   3,   4,
 	   TILE_SIZE_1x1,
 	   HZ_SUBTROPIC | HZ_ZON5 | HZ_ZON4 | HZ_ZON3,
 	   CT_PASSENGERS, CT_MAIL, CT_GOODS), // 5A
-	MS(   0, MAX_YEAR,   8,  90, STR_TOWN_BUILDING_NAME_CHURCH_1,                 200,   3,   2,   0,   0,
+	MS(   0, CalendarTime::MAX_YEAR,   8,  90, STR_TOWN_BUILDING_NAME_CHURCH_1,                 200,   3,   2,   0,   0,
 	   BUILDING_IS_CHURCH | TILE_SIZE_1x1,
 	   HZ_TOYLND | HZ_ZON5 | HZ_ZON4 | HZ_ZON3 | HZ_ZON2 | HZ_ZON1,
 	   CT_PASSENGERS, CT_MAIL, CT_CANDY), // 5B
-	MS(   0, MAX_YEAR,  18,  90, STR_TOWN_BUILDING_NAME_HOUSES_2,                  90,   5,   6,   2,   2,
+	MS(   0, CalendarTime::MAX_YEAR,  18,  90, STR_TOWN_BUILDING_NAME_HOUSES_2,                  90,   5,   6,   2,   2,
 	   TILE_SIZE_1x1,
 	   HZ_TOYLND | HZ_ZON5 | HZ_ZON4 | HZ_ZON3 | HZ_ZON2 | HZ_ZON1,
 	   CT_PASSENGERS, CT_MAIL, CT_CANDY), // 5C
-	MS(   0, MAX_YEAR,   7,  70, STR_TOWN_BUILDING_NAME_HOUSES_2,                  50,   3,   3,   1,   1,
+	MS(   0, CalendarTime::MAX_YEAR,   7,  70, STR_TOWN_BUILDING_NAME_HOUSES_2,                  50,   3,   3,   1,   1,
 	   TILE_SIZE_1x1,
 	   HZ_TOYLND | HZ_ZON2 | HZ_ZON1,
 	   CT_PASSENGERS, CT_MAIL, CT_CANDY), // 5D
-	MS(   0, MAX_YEAR,  15,  80, STR_TOWN_BUILDING_NAME_HOUSES_2,                  75,   6,   3,   1,   2,
+	MS(   0, CalendarTime::MAX_YEAR,  15,  80, STR_TOWN_BUILDING_NAME_HOUSES_2,                  75,   6,   3,   1,   2,
 	   TILE_SIZE_1x1,
 	   HZ_TOYLND | HZ_ZON4 | HZ_ZON3 | HZ_ZON2 | HZ_ZON1,
 	   CT_PASSENGERS, CT_MAIL, CT_CANDY), // 5E
-	MS(   0, MAX_YEAR,  17,  80, STR_TOWN_BUILDING_NAME_HOUSES_2,                  75,   6,   3,   1,   2,
+	MS(   0, CalendarTime::MAX_YEAR,  17,  80, STR_TOWN_BUILDING_NAME_HOUSES_2,                  75,   6,   3,   1,   2,
 	   TILE_SIZE_1x1,
 	   HZ_TOYLND | HZ_ZON4 | HZ_ZON3 | HZ_ZON2 | HZ_ZON1,
 	   CT_PASSENGERS, CT_MAIL, CT_CANDY), // 5F
-	MS(   0, MAX_YEAR,  19,  80, STR_TOWN_BUILDING_NAME_HOUSES_2,                  75,   6,   3,   1,   2,
+	MS(   0, CalendarTime::MAX_YEAR,  19,  80, STR_TOWN_BUILDING_NAME_HOUSES_2,                  75,   6,   3,   1,   2,
 	   TILE_SIZE_1x1,
 	   HZ_TOYLND | HZ_ZON4 | HZ_ZON3 | HZ_ZON2 | HZ_ZON1,
 	   CT_PASSENGERS, CT_MAIL, CT_CANDY), // 60
-	MS(   0, MAX_YEAR,  21,  80, STR_TOWN_BUILDING_NAME_HOUSES_2,                  75,   6,   3,   1,   2,
+	MS(   0, CalendarTime::MAX_YEAR,  21,  80, STR_TOWN_BUILDING_NAME_HOUSES_2,                  75,   6,   3,   1,   2,
 	   TILE_SIZE_1x1,
 	   HZ_TOYLND | HZ_ZON4 | HZ_ZON3 | HZ_ZON2 | HZ_ZON1,
 	   CT_PASSENGERS, CT_MAIL, CT_CANDY), // 61
-	MS(   0, MAX_YEAR,  75, 160, STR_TOWN_BUILDING_NAME_TALL_OFFICE_BLOCK_1,      130,  20,   8,   4,   2,
+	MS(   0, CalendarTime::MAX_YEAR,  75, 160, STR_TOWN_BUILDING_NAME_TALL_OFFICE_BLOCK_1,      130,  20,   8,   4,   2,
 	   TILE_SIZE_1x1,
 	   HZ_TOYLND | HZ_ZON5 | HZ_ZON4 | HZ_ZON3,
 	   CT_PASSENGERS, CT_MAIL, CT_CANDY), // 62
-	MS(   0, MAX_YEAR,  35,  90, STR_TOWN_BUILDING_NAME_HOUSES_2,                  80,   9,   4,   1,   2,
+	MS(   0, CalendarTime::MAX_YEAR,  35,  90, STR_TOWN_BUILDING_NAME_HOUSES_2,                  80,   9,   4,   1,   2,
 	   TILE_SIZE_1x2,
 	   HZ_TOYLND | HZ_ZON5 | HZ_ZON4 | HZ_ZON3 | HZ_ZON2 | HZ_ZON1,
 	   CT_PASSENGERS, CT_MAIL, CT_CANDY), // 63
-	MS(   0, MAX_YEAR,   0,  90, STR_TOWN_BUILDING_NAME_HOUSES_2,                  80,   0,   4,   1,   2,
+	MS(   0, CalendarTime::MAX_YEAR,   0,  90, STR_TOWN_BUILDING_NAME_HOUSES_2,                  80,   0,   4,   1,   2,
 	   TILE_NO_FLAG,
 	   HZ_NOZNS,
 	   CT_PASSENGERS, CT_MAIL, CT_CANDY), // 64
-	MS(   0, MAX_YEAR,  85, 150, STR_TOWN_BUILDING_NAME_TALL_OFFICE_BLOCK_1,      130,  18,   8,   4,   2,
+	MS(   0, CalendarTime::MAX_YEAR,  85, 150, STR_TOWN_BUILDING_NAME_TALL_OFFICE_BLOCK_1,      130,  18,   8,   4,   2,
 	   TILE_SIZE_1x1,
 	   HZ_TOYLND | HZ_ZON5 | HZ_ZON4 | HZ_ZON3,
 	   CT_PASSENGERS, CT_MAIL, CT_CANDY), // 65
-	MS(   0, MAX_YEAR,  11,  60, STR_TOWN_BUILDING_NAME_IGLOO_1,                   45,   3,   3,   1,   1,
+	MS(   0, CalendarTime::MAX_YEAR,  11,  60, STR_TOWN_BUILDING_NAME_IGLOO_1,                   45,   3,   3,   1,   1,
 	   TILE_SIZE_1x1,
 	   HZ_TOYLND | HZ_ZON1,
 	   CT_PASSENGERS, CT_MAIL, CT_CANDY), // 66
-	MS(   0, MAX_YEAR,  10,  60, STR_TOWN_BUILDING_NAME_TEPEES_1,                  45,   3,   3,   1,   1,
+	MS(   0, CalendarTime::MAX_YEAR,  10,  60, STR_TOWN_BUILDING_NAME_TEPEES_1,                  45,   3,   3,   1,   1,
 	   TILE_SIZE_1x1,
 	   HZ_TOYLND | HZ_ZON1,
 	   CT_PASSENGERS, CT_MAIL, CT_CANDY), // 67
-	MS(   0, MAX_YEAR,  67, 140, STR_TOWN_BUILDING_NAME_SHOPS_AND_OFFICES_1,      130,  22,   8,   4,   4,
+	MS(   0, CalendarTime::MAX_YEAR,  67, 140, STR_TOWN_BUILDING_NAME_SHOPS_AND_OFFICES_1,      130,  22,   8,   4,   4,
 	   TILE_SIZE_1x1,
 	   HZ_TOYLND | HZ_ZON5 | HZ_ZON4 | HZ_ZON3,
 	   CT_PASSENGERS, CT_MAIL, CT_FIZZY_DRINKS), // 68
-	MS(   0, MAX_YEAR,  86, 145, STR_TOWN_BUILDING_NAME_SHOPS_AND_OFFICES_1,      130,  23,   8,   4,   4,
+	MS(   0, CalendarTime::MAX_YEAR,  86, 145, STR_TOWN_BUILDING_NAME_SHOPS_AND_OFFICES_1,      130,  23,   8,   4,   4,
 	   TILE_SIZE_1x1,
 	   HZ_TOYLND | HZ_ZON5 | HZ_ZON4 | HZ_ZON3,
 	   CT_PASSENGERS, CT_MAIL, CT_FIZZY_DRINKS), // 69
-	MS(   0, MAX_YEAR,  95, 165, STR_TOWN_BUILDING_NAME_TALL_OFFICE_BLOCK_1,      130,  28,   8,   4,   2,
+	MS(   0, CalendarTime::MAX_YEAR,  95, 165, STR_TOWN_BUILDING_NAME_TALL_OFFICE_BLOCK_1,      130,  28,   8,   4,   2,
 	   TILE_SIZE_1x1,
 	   HZ_TOYLND | HZ_ZON5 | HZ_ZON4 | HZ_ZON3,
 	   CT_PASSENGERS, CT_MAIL, CT_CANDY), // 6A
-	MS(   0, MAX_YEAR,  30,  90, STR_TOWN_BUILDING_NAME_STATUE_1,                  70,  10,   4,   1,   2,
+	MS(   0, CalendarTime::MAX_YEAR,  30,  90, STR_TOWN_BUILDING_NAME_STATUE_1,                  70,  10,   4,   1,   2,
 	   TILE_SIZE_1x1,
 	   HZ_TOYLND | HZ_ZON5 | HZ_ZON4 | HZ_ZON3,
 	   CT_PASSENGERS, CT_MAIL, CT_CANDY), // 6B
-	MS(   0, MAX_YEAR,  25,  75, STR_TOWN_BUILDING_NAME_TEAPOT_HOUSE_1,            65,   8,   3,   1,   2,
+	MS(   0, CalendarTime::MAX_YEAR,  25,  75, STR_TOWN_BUILDING_NAME_TEAPOT_HOUSE_1,            65,   8,   3,   1,   2,
 	   TILE_SIZE_1x1,
 	   HZ_TOYLND | HZ_ZON5 | HZ_ZON4 | HZ_ZON3 | HZ_ZON2 | HZ_ZON1,
 	   CT_PASSENGERS, CT_MAIL, CT_CANDY), // 6C
-	MS(   0, MAX_YEAR,  18,  85, STR_TOWN_BUILDING_NAME_PIGGY_BANK_1,              95,   7,   3,   2,   4,
+	MS(   0, CalendarTime::MAX_YEAR,  18,  85, STR_TOWN_BUILDING_NAME_PIGGY_BANK_1,              95,   7,   3,   2,   4,
 	   TILE_SIZE_1x1,
 	   HZ_TOYLND | HZ_ZON5 | HZ_ZON4 | HZ_ZON3 | HZ_ZON2 | HZ_ZON1,
 	   CT_PASSENGERS, CT_MAIL, CT_FIZZY_DRINKS), // 6D
diff --git a/src/timer/timer_game_calendar.cpp b/src/timer/timer_game_calendar.cpp
--- a/src/timer/timer_game_calendar.cpp
+++ b/src/timer/timer_game_calendar.cpp
@@ -68,42 +68,42 @@ static const uint16_t _accum_days_for_mo
  * @param date the date to convert from
  * @param ymd  the year, month and day to write to
  */
-/* static */ void TimerGameCalendar::ConvertDateToYMD(TimerGameCalendar::Date date, YearMonthDay *ymd)
+/* static */ void TimerGameCalendar::ConvertDateToYMD(TimerGameCalendar::Date date, TimerGameCalendar::YearMonthDay *ymd)
 {
 	/* Year determination in multiple steps to account for leap
 	 * years. First do the large steps, then the smaller ones.
 	 */
 
 	/* There are 97 leap years in 400 years */
-	TimerGameCalendar::Year yr = 400 * (static_cast<int32_t>(date) / (DAYS_IN_YEAR * 400 + 97));
-	int rem = static_cast<int32_t>(date) % (DAYS_IN_YEAR * 400 + 97);
+	TimerGameCalendar::Year yr = 400 * (static_cast<int32_t>(date) / (CalendarTime::DAYS_IN_YEAR * 400 + 97));
+	int rem = static_cast<int32_t>(date) % (CalendarTime::DAYS_IN_YEAR * 400 + 97);
 	uint16_t x;
 
-	if (rem >= DAYS_IN_YEAR * 100 + 25) {
+	if (rem >= CalendarTime::DAYS_IN_YEAR * 100 + 25) {
 		/* There are 25 leap years in the first 100 years after
 		 * every 400th year, as every 400th year is a leap year */
 		yr += 100;
-		rem -= DAYS_IN_YEAR * 100 + 25;
+		rem -= CalendarTime::DAYS_IN_YEAR * 100 + 25;
 
 		/* There are 24 leap years in the next couple of 100 years */
-		yr += 100 * (rem / (DAYS_IN_YEAR * 100 + 24));
-		rem = (rem % (DAYS_IN_YEAR * 100 + 24));
+		yr += 100 * (rem / (CalendarTime::DAYS_IN_YEAR * 100 + 24));
+		rem = (rem % (CalendarTime::DAYS_IN_YEAR * 100 + 24));
 	}
 
-	if (!TimerGameCalendar::IsLeapYear(yr) && rem >= DAYS_IN_YEAR * 4) {
+	if (!TimerGameCalendar::IsLeapYear(yr) && rem >= CalendarTime::DAYS_IN_YEAR * 4) {
 		/* The first 4 year of the century are not always a leap year */
 		yr += 4;
-		rem -= DAYS_IN_YEAR * 4;
+		rem -= CalendarTime::DAYS_IN_YEAR * 4;
 	}
 
 	/* There is 1 leap year every 4 years */
-	yr += 4 * (rem / (DAYS_IN_YEAR * 4 + 1));
-	rem = rem % (DAYS_IN_YEAR * 4 + 1);
+	yr += 4 * (rem / (CalendarTime::DAYS_IN_YEAR * 4 + 1));
+	rem = rem % (CalendarTime::DAYS_IN_YEAR * 4 + 1);
 
 	/* The last (max 3) years to account for; the first one
 	 * can be, but is not necessarily a leap year */
-	while (rem >= (TimerGameCalendar::IsLeapYear(yr) ? DAYS_IN_LEAP_YEAR : DAYS_IN_YEAR)) {
-		rem -= TimerGameCalendar::IsLeapYear(yr) ? DAYS_IN_LEAP_YEAR : DAYS_IN_YEAR;
+	while (rem >= (TimerGameCalendar::IsLeapYear(yr) ? CalendarTime::DAYS_IN_LEAP_YEAR : CalendarTime::DAYS_IN_YEAR)) {
+		rem -= TimerGameCalendar::IsLeapYear(yr) ? CalendarTime::DAYS_IN_LEAP_YEAR : CalendarTime::DAYS_IN_YEAR;
 		yr++;
 	}
 
@@ -131,7 +131,7 @@ static const uint16_t _accum_days_for_mo
 	/* Account for the missing of the 29th of February in non-leap years */
 	if (!TimerGameCalendar::IsLeapYear(year) && days >= ACCUM_MAR) days--;
 
-	return DateAtStartOfYear(year) + days;
+	return TimerGameCalendar::DateAtStartOfYear(year) + days;
 }
 
 /**
@@ -153,7 +153,7 @@ static const uint16_t _accum_days_for_mo
 {
 	assert(fract < Ticks::DAY_TICKS);
 
-	YearMonthDay ymd;
+	TimerGameCalendar::YearMonthDay ymd;
 
 	TimerGameCalendar::date = date;
 	TimerGameCalendar::date_fract = fract;
@@ -240,11 +240,11 @@ void TimerManager<TimerGameCalendar>::El
 	}
 
 	/* check if we reached the maximum year, decrement dates by a year */
-	if (TimerGameCalendar::year == MAX_YEAR + 1) {
+	if (TimerGameCalendar::year == CalendarTime::MAX_YEAR + 1) {
 		int days_this_year;
 
 		TimerGameCalendar::year--;
-		days_this_year = TimerGameCalendar::IsLeapYear(TimerGameCalendar::year) ? DAYS_IN_LEAP_YEAR : DAYS_IN_YEAR;
+		days_this_year = TimerGameCalendar::IsLeapYear(TimerGameCalendar::year) ? CalendarTime::DAYS_IN_LEAP_YEAR : CalendarTime::DAYS_IN_YEAR;
 		TimerGameCalendar::date -= days_this_year;
 		for (Vehicle *v : Vehicle::Iterate()) v->ShiftDates(-days_this_year);
 		for (LinkGraph *lg : LinkGraph::Iterate()) lg->ShiftDates(-days_this_year);
diff --git a/src/timer/timer_game_calendar.h b/src/timer/timer_game_calendar.h
--- a/src/timer/timer_game_calendar.h
+++ b/src/timer/timer_game_calendar.h
@@ -33,6 +33,29 @@
  */
 class TimerGameCalendar {
 public:
+	/** The type to store our dates in. */
+	using Date = StrongType::Typedef<int32_t, struct DateTag, StrongType::Compare, StrongType::Integer>;
+
+	/** The fraction of a date we're in, i.e. the number of ticks since the last date changeover. */
+	using DateFract = uint16_t;
+
+	/** Type for the year, note: 0 based, i.e. starts at the year 0. */
+	using Year = StrongType::Typedef<int32_t, struct YearTag, StrongType::Compare, StrongType::Integer>;
+	/** Type for the month, note: 0 based, i.e. 0 = January, 11 = December. */
+	using Month = uint8_t;
+	/** Type for the day of the month, note: 1 based, first day of a month is 1. */
+	using Day = uint8_t;
+
+	/**
+	 * Data structure to convert between Date and triplet (year, month, and day).
+	 * @see TimerGameCalendar::ConvertDateToYMD(), TimerGameCalendar::ConvertYMDToDate()
+	 */
+	struct YearMonthDay {
+		Year  year;   ///< Year (0...)
+		Month month;  ///< Month (0..11)
+		Day   day;    ///< Day (1..31)
+	};
+
 	enum Trigger {
 		DAY,
 		WEEK,
@@ -77,33 +100,35 @@ public:
 	struct TStorage {
 	};
 
-	/** The type to store our dates in. */
-	using Date = StrongType::Typedef<int32_t, struct DateTag, StrongType::Compare, StrongType::Integer>;
-
-	/** The fraction of a date we're in, i.e. the number of ticks since the last date changeover. */
-	using DateFract = uint16_t;
-
-	/** Type for the year, note: 0 based, i.e. starts at the year 0. */
-	using Year = StrongType::Typedef<int32_t, struct YearTag, StrongType::Compare, StrongType::Integer>;
-	/** Type for the month, note: 0 based, i.e. 0 = January, 11 = December. */
-	using Month = uint8_t;
-	/** Type for the day of the month, note: 1 based, first day of a month is 1. */
-	using Day = uint8_t;
+	static bool IsLeapYear(Year yr);
+	static void ConvertDateToYMD(Date date, YearMonthDay * ymd);
+	static Date ConvertYMDToDate(Year year, Month month, Day day);
+	static void SetDate(Date date, DateFract fract);
 
 	/**
-	 * Data structure to convert between Date and triplet (year, month, and day).
-	 * @see TimerGameCalendar::ConvertDateToYMD(), TimerGameCalendar::ConvertYMDToDate()
-	 */
-	struct YearMonthDay {
-		Year  year;   ///< Year (0...)
-		Month month;  ///< Month (0..11)
-		Day   day;    ///< Day (1..31)
-	};
+	* Calculate the year of a given date.
+	* @param date The date to consider.
+	* @return the year.
+	*/
+	static constexpr Year DateToYear(Date date)
+	{
+		/* Hardcode the number of days in a year because we can't access CalendarTime from here. */
+		return static_cast<int32_t>(date) / 366;
+	}
 
-	static bool IsLeapYear(TimerGameCalendar::Year yr);
-	static void ConvertDateToYMD(TimerGameCalendar::Date date, YearMonthDay *ymd);
-	static TimerGameCalendar::Date ConvertYMDToDate(TimerGameCalendar::Year year, TimerGameCalendar::Month month, TimerGameCalendar::Day day);
-	static void SetDate(TimerGameCalendar::Date date, TimerGameCalendar::DateFract fract);
+	/**
+	* Calculate the date of the first day of a given year.
+	* @param year the year to get the first day of.
+	* @return the date.
+	*/
+	static constexpr Date DateAtStartOfYear(Year year)
+	{
+		int32_t year_as_int = static_cast<int32_t>(year);
+		uint number_of_leap_years = (year == 0) ? 0 : ((year_as_int - 1) / 4 - (year_as_int - 1) / 100 + (year_as_int - 1) / 400 + 1);
+
+		/* Hardcode the number of days in a year because we can't access CalendarTime from here. */
+		return (365 * year_as_int) + number_of_leap_years;
+	}
 
 	static Year year; ///< Current year, starting at 0.
 	static Month month; ///< Current month (0..11).
@@ -111,4 +136,53 @@ public:
 	static DateFract date_fract; ///< Fractional part of the day.
 };
 
+/**
+ * Storage class for Calendar time constants.
+ */
+class CalendarTime {
+public:
+	static constexpr int DAYS_IN_YEAR = 365; ///< days per year
+	static constexpr int DAYS_IN_LEAP_YEAR = 366; ///< sometimes, you need one day more...
+	static constexpr int MONTHS_IN_YEAR = 12; ///< months per year
+
+	static constexpr int SECONDS_PER_DAY = 2;   ///< approximate seconds per day, not for precise calculations
+
+	/*
+	 * ORIGINAL_BASE_YEAR, ORIGINAL_MAX_YEAR and DAYS_TILL_ORIGINAL_BASE_YEAR are
+	 * primarily used for loading newgrf and savegame data and returning some
+	 * newgrf (callback) functions that were in the original (TTD) inherited
+	 * format, where 'TimerGameCalendar::date == 0' meant that it was 1920-01-01.
+	 */
+
+	/** The minimum starting year/base year of the original TTD */
+	static constexpr TimerGameCalendar::Year ORIGINAL_BASE_YEAR = 1920;
+	/** The original ending year */
+	static constexpr TimerGameCalendar::Year ORIGINAL_END_YEAR = 2051;
+	/** The maximum year of the original TTD */
+	static constexpr TimerGameCalendar::Year ORIGINAL_MAX_YEAR = 2090;
+
+	/** The absolute minimum & maximum years in OTTD */
+	static constexpr TimerGameCalendar::Year MIN_YEAR = 0;
+
+	/** The default starting year */
+	static constexpr TimerGameCalendar::Year DEF_START_YEAR = 1950;
+	/** The default scoring end year */
+	static constexpr TimerGameCalendar::Year DEF_END_YEAR = ORIGINAL_END_YEAR - 1;
+
+	/**
+	 * MAX_YEAR, nicely rounded value of the number of years that can
+	 * be encoded in a single 32 bits date, about 2^31 / 366 years.
+	 */
+	static constexpr TimerGameCalendar::Year MAX_YEAR = 5000000;
+
+	/** The date of the first day of the original base year. */
+	static constexpr TimerGameCalendar::Date DAYS_TILL_ORIGINAL_BASE_YEAR = TimerGameCalendar::DateAtStartOfYear(ORIGINAL_BASE_YEAR);
+
+	/** The date of the last day of the max year. */
+	static constexpr TimerGameCalendar::Date MAX_DATE = TimerGameCalendar::DateAtStartOfYear(CalendarTime::MAX_YEAR + 1) - 1;
+
+	static constexpr TimerGameCalendar::Year INVALID_YEAR = -1; ///< Representation of an invalid year
+	static constexpr TimerGameCalendar::Date INVALID_DATE = -1; ///< Representation of an invalid date
+};
+
 #endif /* TIMER_GAME_CALENDAR_H */
diff --git a/src/timetable_cmd.cpp b/src/timetable_cmd.cpp
--- a/src/timetable_cmd.cpp
+++ b/src/timetable_cmd.cpp
@@ -304,11 +304,11 @@ CommandCost CmdSetTimetableStart(DoComma
 	int total_duration = v->orders->GetTimetableTotalDuration();
 
 	/* Don't let a timetable start more than 15 years into the future or 1 year in the past. */
-	if (start_date < 0 || start_date > MAX_DATE) return CMD_ERROR;
-	if (start_date - TimerGameCalendar::date > DateAtStartOfYear(MAX_TIMETABLE_START_YEARS)) return CMD_ERROR;
-	if (TimerGameCalendar::date - start_date > DAYS_IN_LEAP_YEAR) return CMD_ERROR;
+	if (start_date < 0 || start_date > CalendarTime::MAX_DATE) return CMD_ERROR;
+	if (start_date - TimerGameCalendar::date > TimerGameCalendar::DateAtStartOfYear(MAX_TIMETABLE_START_YEARS)) return CMD_ERROR;
+	if (TimerGameCalendar::date - start_date > CalendarTime::DAYS_IN_LEAP_YEAR) return CMD_ERROR;
 	if (timetable_all && !v->orders->IsCompleteTimetable()) return CommandCost(STR_ERROR_TIMETABLE_INCOMPLETE);
-	if (timetable_all && start_date + total_duration / Ticks::DAY_TICKS > MAX_DATE) return CMD_ERROR;
+	if (timetable_all && start_date + total_duration / Ticks::DAY_TICKS > CalendarTime::MAX_DATE) return CMD_ERROR;
 
 	if (flags & DC_EXEC) {
 		std::vector<Vehicle *> vehs;
@@ -494,7 +494,7 @@ void UpdateVehicleTimetable(Vehicle *v, 
 	 * check how many ticks the (fully filled) timetable has. If a timetable cycle is
 	 * shorter than the amount of ticks we are late we reduce the lateness by the
 	 * length of a full cycle till lateness is less than the length of a timetable
-	 * cycle. When the timetable isn't fully filled the cycle will be Tick::INVALID_TICKS. */
+	 * cycle. When the timetable isn't fully filled the cycle will be Ticks::INVALID_TICKS. */
 	if (v->lateness_counter > (int)timetabled) {
 		TimerGameTick::Ticks cycle = v->orders->GetTimetableTotalDuration();
 		if (cycle != Ticks::INVALID_TICKS && v->lateness_counter > cycle) {
diff --git a/src/timetable_gui.cpp b/src/timetable_gui.cpp
--- a/src/timetable_gui.cpp
+++ b/src/timetable_gui.cpp
@@ -194,7 +194,7 @@ struct TimetableWindow : Window {
 	{
 		switch (widget) {
 			case WID_VT_ARRIVAL_DEPARTURE_PANEL:
-				SetDParamMaxValue(1, DateAtStartOfYear(MAX_YEAR), 0, FS_SMALL);
+				SetDParamMaxValue(1, TimerGameCalendar::DateAtStartOfYear(CalendarTime::MAX_YEAR), 0, FS_SMALL);
 				size->width = std::max(GetStringBoundingBox(STR_TIMETABLE_ARRIVAL).width, GetStringBoundingBox(STR_TIMETABLE_DEPARTURE).width) + WidgetDimensions::scaled.hsep_wide + padding.width;
 				FALLTHROUGH;
 
diff --git a/src/toolbar_gui.cpp b/src/toolbar_gui.cpp
--- a/src/toolbar_gui.cpp
+++ b/src/toolbar_gui.cpp
@@ -1148,7 +1148,7 @@ void ToggleDirtyBlocks()
  */
 void SetStartingYear(TimerGameCalendar::Year year)
 {
-	_settings_game.game_creation.starting_year = Clamp(year, MIN_YEAR, MAX_YEAR);
+	_settings_game.game_creation.starting_year = Clamp(year, CalendarTime::MIN_YEAR, CalendarTime::MAX_YEAR);
 	TimerGameCalendar::Date new_date = TimerGameCalendar::ConvertYMDToDate(_settings_game.game_creation.starting_year, 0, 1);
 	/* If you open a savegame as scenario there may already be link graphs.*/
 	LinkGraphSchedule::instance.ShiftDates(new_date - TimerGameCalendar::date);
@@ -2357,8 +2357,8 @@ struct ScenarioEditorToolbarWindow : Win
 
 	void OnPaint() override
 	{
-		this->SetWidgetDisabledState(WID_TE_DATE_BACKWARD, _settings_game.game_creation.starting_year <= MIN_YEAR);
-		this->SetWidgetDisabledState(WID_TE_DATE_FORWARD, _settings_game.game_creation.starting_year >= MAX_YEAR);
+		this->SetWidgetDisabledState(WID_TE_DATE_BACKWARD, _settings_game.game_creation.starting_year <= CalendarTime::MIN_YEAR);
+		this->SetWidgetDisabledState(WID_TE_DATE_FORWARD, _settings_game.game_creation.starting_year >= CalendarTime::MAX_YEAR);
 		this->SetWidgetDisabledState(WID_TE_ROADS, (GetRoadTypes(true) & ~_roadtypes_type) == ROADTYPES_NONE);
 		this->SetWidgetDisabledState(WID_TE_TRAMS, (GetRoadTypes(true) & _roadtypes_type) == ROADTYPES_NONE);
 
@@ -2398,7 +2398,7 @@ struct ScenarioEditorToolbarWindow : Win
 				break;
 
 			case WID_TE_DATE:
-				SetDParam(0, TimerGameCalendar::ConvertYMDToDate(MAX_YEAR, 0, 1));
+				SetDParam(0, TimerGameCalendar::ConvertYMDToDate(CalendarTime::MAX_YEAR, 0, 1));
 				*size = GetStringBoundingBox(STR_JUST_DATE_LONG);
 				break;
 		}
@@ -2512,7 +2512,7 @@ struct ScenarioEditorToolbarWindow : Win
 			value = atoi(str);
 		} else {
 			/* An empty string means revert to the default */
-			value = static_cast<int32_t>(DEF_START_YEAR);
+			value = static_cast<int32_t>(CalendarTime::DEF_START_YEAR);
 		}
 		SetStartingYear(value);
 
diff --git a/src/town_cmd.cpp b/src/town_cmd.cpp
--- a/src/town_cmd.cpp
+++ b/src/town_cmd.cpp
@@ -871,7 +871,7 @@ RoadType GetTownRoadType(const Town *t)
 		if (!HasBit(rti->flags, ROTF_TOWN_BUILD)) continue;
 
 		/* Not yet introduced at this date. */
-		if (IsInsideMM(rti->introduction_date, 0, static_cast<int32_t>(MAX_DATE)) && rti->introduction_date > TimerGameCalendar::date) continue;
+		if (IsInsideMM(rti->introduction_date, 0, static_cast<int32_t>(CalendarTime::MAX_DATE)) && rti->introduction_date > TimerGameCalendar::date) continue;
 
 		if (best != nullptr) {
 			if ((rti->max_speed == 0 ? assume_max_speed : rti->max_speed) < (best->max_speed == 0 ? assume_max_speed : best->max_speed)) continue;
diff --git a/src/train_cmd.cpp b/src/train_cmd.cpp
--- a/src/train_cmd.cpp
+++ b/src/train_cmd.cpp
@@ -4179,7 +4179,7 @@ void Train::OnNewDay()
 
 		if (this->running_ticks != 0) {
 			/* running costs */
-			CommandCost cost(EXPENSES_TRAIN_RUN, this->GetRunningCost() * this->running_ticks / (DAYS_IN_YEAR  * Ticks::DAY_TICKS));
+			CommandCost cost(EXPENSES_TRAIN_RUN, this->GetRunningCost() * this->running_ticks / (CalendarTime::DAYS_IN_YEAR  * Ticks::DAY_TICKS));
 
 			this->profit_this_year -= cost.GetCost();
 			this->running_ticks = 0;
diff --git a/src/vehicle.cpp b/src/vehicle.cpp
--- a/src/vehicle.cpp
+++ b/src/vehicle.cpp
@@ -1369,7 +1369,7 @@ bool Vehicle::HandleBreakdown()
  */
 void AgeVehicle(Vehicle *v)
 {
-	if (v->age < MAX_DATE) {
+	if (v->age < CalendarTime::MAX_DATE) {
 		v->age++;
 		if (v->IsPrimaryVehicle() && v->age == VEHICLE_PROFIT_MIN_AGE + 1) GroupStatistics::VehicleReachedMinAge(v);
 	}
@@ -1378,7 +1378,7 @@ void AgeVehicle(Vehicle *v)
 
 	auto age = v->age - v->max_age;
 	for (int32_t i = 0; i <= 4; i++) {
-		if (age == DateAtStartOfYear(i)) {
+		if (age == TimerGameCalendar::DateAtStartOfYear(i)) {
 			v->reliability_spd_dec <<= 1;
 			break;
 		}
@@ -1396,11 +1396,11 @@ void AgeVehicle(Vehicle *v)
 	if (EngineHasReplacementForCompany(c, v->engine_type, v->group_id)) return;
 
 	StringID str;
-	if (age == DateAtStartOfYear(-1)) {
+	if (age == TimerGameCalendar::DateAtStartOfYear(-1)) {
 		str = STR_NEWS_VEHICLE_IS_GETTING_OLD;
-	} else if (age == DateAtStartOfYear(0)) {
+	} else if (age == TimerGameCalendar::DateAtStartOfYear(0)) {
 		str = STR_NEWS_VEHICLE_IS_GETTING_VERY_OLD;
-	} else if (age > DateAtStartOfYear(0) && (static_cast<int32_t>(age) % DAYS_IN_LEAP_YEAR) == 0) {
+	} else if (age > TimerGameCalendar::DateAtStartOfYear(0) && (static_cast<int32_t>(age) % CalendarTime::DAYS_IN_LEAP_YEAR) == 0) {
 		str = STR_NEWS_VEHICLE_IS_GETTING_VERY_OLD_AND;
 	} else {
 		return;
diff --git a/src/vehicle_func.h b/src/vehicle_func.h
--- a/src/vehicle_func.h
+++ b/src/vehicle_func.h
@@ -25,7 +25,7 @@
 #define IS_CUSTOM_FIRSTHEAD_SPRITE(x) (x == 0xFD)
 #define IS_CUSTOM_SECONDHEAD_SPRITE(x) (x == 0xFE)
 
-static const int VEHICLE_PROFIT_MIN_AGE = DAYS_IN_YEAR * 2; ///< Only vehicles older than this have a meaningful profit.
+static const int VEHICLE_PROFIT_MIN_AGE = CalendarTime::DAYS_IN_YEAR * 2; ///< Only vehicles older than this have a meaningful profit.
 static const Money VEHICLE_PROFIT_THRESHOLD = 10000;        ///< Threshold for a vehicle to be considered making good profit.
 
 /**
diff --git a/src/vehicle_gui.cpp b/src/vehicle_gui.cpp
--- a/src/vehicle_gui.cpp
+++ b/src/vehicle_gui.cpp
@@ -1733,7 +1733,7 @@ void BaseVehicleListWindow::DrawVehicleL
 				if (v->IsChainInDepot()) {
 					tc = TC_BLUE;
 				} else {
-					tc = (v->age > v->max_age - DAYS_IN_LEAP_YEAR) ? TC_RED : TC_BLACK;
+					tc = (v->age > v->max_age - CalendarTime::DAYS_IN_LEAP_YEAR) ? TC_RED : TC_BLACK;
 				}
 
 				SetDParam(0, v->unitnumber);
@@ -2438,7 +2438,7 @@ struct VehicleDetailsWindow : Window {
 
 			case WID_VD_SERVICING_INTERVAL:
 				SetDParamMaxValue(0, MAX_SERVINT_DAYS); // Roughly the maximum interval
-				SetDParamMaxValue(1, DateAtStartOfYear(MAX_YEAR)); // Roughly the maximum year
+				SetDParamMaxValue(1, TimerGameCalendar::DateAtStartOfYear(CalendarTime::MAX_YEAR)); // Roughly the maximum year
 				size->width = std::max(
 					GetStringBoundingBox(STR_VEHICLE_DETAILS_SERVICING_INTERVAL_PERCENT).width,
 					GetStringBoundingBox(STR_VEHICLE_DETAILS_SERVICING_INTERVAL_DAYS).width
@@ -2495,9 +2495,9 @@ struct VehicleDetailsWindow : Window {
 				Rect tr = r.Shrink(WidgetDimensions::scaled.framerect);
 
 				/* Draw running cost */
-				SetDParam(1, DateToYear(v->age));
-				SetDParam(0, (v->age + DAYS_IN_YEAR < v->max_age) ? STR_VEHICLE_INFO_AGE : STR_VEHICLE_INFO_AGE_RED);
-				SetDParam(2, DateToYear(v->max_age));
+				SetDParam(1, TimerGameCalendar::DateToYear(v->age));
+				SetDParam(0, (v->age + CalendarTime::DAYS_IN_YEAR < v->max_age) ? STR_VEHICLE_INFO_AGE : STR_VEHICLE_INFO_AGE_RED);
+				SetDParam(2, TimerGameCalendar::DateToYear(v->max_age));
 				SetDParam(3, v->GetDisplayRunningCost());
 				DrawString(tr, STR_VEHICLE_INFO_AGE_RUNNING_COST_YR);
 				tr.top += FONT_HEIGHT_NORMAL;