diff --git a/src/date_type.h b/src/date_type.h
--- a/src/date_type.h
+++ b/src/date_type.h
@@ -28,6 +28,7 @@ typedef uint8  Day;   ///< Type for the 
 static const int DAY_TICKS         =  74; ///< ticks per day
 static const int DAYS_IN_YEAR      = 365; ///< days per year
 static const int DAYS_IN_LEAP_YEAR = 366; ///< sometimes, you need one day more...
+static const int MONTHS_IN_YEAR    =  12; ///< months per year
 
 static const int STATION_RATING_TICKS     = 185; ///< cycle duration for updating station rating
 static const int STATION_ACCEPTANCE_TICKS = 250; ///< cycle duration for updating station acceptance