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
@@ -20,7 +20,7 @@
 #include "../subsidy_base.h"
 #include "../debug.h"
 #include "../depot_base.h"
-#include "../date_func.h"
+#include "../timer/timer_game_calendar.h"
 #include "../timer/timer_game_calendar.h"
 #include "../vehicle_func.h"
 #include "../effectvehicle_base.h"
@@ -400,7 +400,7 @@ 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, ConvertYMDToDate(2050, 0, 1));
+	TimerGameCalendar::Date aging_date = std::min(TimerGameCalendar::date + DAYS_TILL_ORIGINAL_BASE_YEAR, TimerGameCalendar::ConvertYMDToDate(2050, 0, 1));
 
 	for (EngineID i = 0; i < 256; i++) {
 		int oi = ttd_to_tto[i];
@@ -847,8 +847,8 @@ static bool LoadOldIndustry(LoadgameStat
 			if (i->type > 0x06) i->type++; // Printing Works were added
 			if (i->type == 0x0A) i->type = 0x12; // Iron Ore Mine has different ID
 
-			YearMonthDay ymd;
-			ConvertDateToYMD(TimerGameCalendar::date, &ymd);
+			TimerGameCalendar::YearMonthDay ymd;
+			TimerGameCalendar::ConvertDateToYMD(TimerGameCalendar::date, &ymd);
 			i->last_prod_year = ymd.year;
 
 			i->random_colour = RemapTTOColour(i->random_colour);