Codechange: use Date/Year constructor explicitly

src/timer/timer_game_common.h

@@ -77,7 +77,7 @@ public:
 	static constexpr Year DateToYear(Date date)
 	{
 		/* Hardcode the number of days in a year because we can't access CalendarTime from here. */
-		return date.base() / 366;
+		return Year{date.base() / 366};
 	}
 
 	/**
@@ -88,10 +88,10 @@ public:
 	static constexpr Date DateAtStartOfYear(Year year)
 	{
 		int32_t year_as_int = year.base();
-		uint number_of_leap_years = (year == 0) ? 0 : ((year_as_int - 1) / 4 - (year_as_int - 1) / 100 + (year_as_int - 1) / 400 + 1);
+		int32_t 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;
+		return Date{(365 * year_as_int) + number_of_leap_years};
 	}
 
 	enum Trigger {