Replace DATE_UNIT_SIZE macro with a function

src/date_func.h

@@ -101,6 +101,15 @@ inline DateTicks NowDateTicks()
 	return DateToDateTicks(_date, _date_fract);
 }
 
+inline Ticks TimetableDisplayUnitSize()
+{
+	if (_settings_time.time_in_minutes) {
+		return _settings_time.ticks_per_minute;
+	} else {
+		return DAY_TICKS * _settings_game.economy.day_length_factor;
+	}
+}
+
 struct debug_date_dumper {
 	const char *HexDate(Date date, DateFract date_fract, uint8_t tick_skip_counter);