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 */