diff --git a/src/date_func.h b/src/date_func.h
deleted file mode 100644
--- a/src/date_func.h
+++ /dev/null
@@ -1,28 +0,0 @@
-/*
- * This file is part of OpenTTD.
- * OpenTTD is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, version 2.
- * OpenTTD is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
- * See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with OpenTTD. If not, see <http://www.gnu.org/licenses/>.
- */
-
-/** @file date_func.h Functions related to dates. */
-
-#ifndef DATE_FUNC_H
-#define DATE_FUNC_H
-
-#include "date_type.h"
-
-void ConvertDateToYMD(TimerGameCalendar::Date date, YearMonthDay *ymd);
-TimerGameCalendar::Date ConvertYMDToDate(TimerGameCalendar::Year year, TimerGameCalendar::Month month, TimerGameCalendar::Day day);
-
-/**
- * Checks whether the given year is a leap year or not.
- * @param yr The year to check.
- * @return True if \c yr is a leap year, otherwise false.
- */
-static inline bool IsLeapYear(TimerGameCalendar::Year yr)
-{
-	return yr % 4 == 0 && (yr % 100 != 0 || yr % 400 == 0);
-}
-
-#endif /* DATE_FUNC_H */