diff --git a/src/timer/timer_game_calendar.cpp b/src/timer/timer_game_calendar.cpp
index 3b7bc870a8..30f938464c 100644
--- a/src/timer/timer_game_calendar.cpp
+++ b/src/timer/timer_game_calendar.cpp
@@ -105,10 +105,13 @@ bool TimerManager<TimerGameCalendar>::Elapsed([[maybe_unused]] TimerGameCalendar
 
 	/* If we are using a non-default calendar progression speed, we need to check the sub_date_fract before updating date_fract. */
 	if (_settings_game.economy.minutes_per_calendar_year != CalendarTime::DEF_MINUTES_PER_YEAR) {
-		TimerGameCalendar::sub_date_fract++;
+		TimerGameCalendar::sub_date_fract += Ticks::DAY_TICKS;
 
 		/* Check if we are ready to increment date_fract */
-		if (TimerGameCalendar::sub_date_fract < (Ticks::DAY_TICKS * _settings_game.economy.minutes_per_calendar_year) / CalendarTime::DEF_MINUTES_PER_YEAR) return false;
+		const uint16_t threshold = (_settings_game.economy.minutes_per_calendar_year * Ticks::DAY_TICKS) / CalendarTime::DEF_MINUTES_PER_YEAR;
+		if (TimerGameCalendar::sub_date_fract < threshold) return false;
+
+		TimerGameCalendar::sub_date_fract = std::min<uint16_t>(TimerGameCalendar::sub_date_fract - threshold, Ticks::DAY_TICKS - 1);
 	}
 
 	TimerGameCalendar::date_fract++;