gistfile1.txt

diff --git a/src/timer/timer_game_calendar.h b/src/timer/timer_game_calendar.h
index de8c78a8ec..7c9763300d 100644
--- a/src/timer/timer_game_calendar.h
+++ b/src/timer/timer_game_calendar.h
@@ -109,6 +109,19 @@ public:
        static Month month; ///< Current month (0..11).
        static Date date; ///< Current date in days (day counter).
        static DateFract date_fract; ///< Fractional part of the day.
+
+       static const int DAYS_IN_YEAR = 365;
+       static constexpr Year ORIGINAL_BASE_YEAR = 1920;
+       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);
+
+               return (DAYS_IN_YEAR * year_as_int) + number_of_leap_years;
+       }
+       static constexpr Date DAYS_TILL_ORIGINAL_BASE_YEAR;
 };
 
+static constexpr TimerGameCalendar::Date DAYS_TILL_ORIGINAL_BASE_YEAR = TimerGameCalendar::DateAtStartOfYear(TimerGameCalendar::ORIGINAL_BASE_YEAR);
+
 #endif /* TIMER_GAME_CALENDAR_H */