Fan.Sys.DateTime.isLeapYear C# (CSharp) Method

        public static bool isLeapYear(int year)
        {
            if ((year & 3) != 0) return false;
              return (year % 100 != 0) || (year % 400 == 0);
        }

 private static int numDaysInMon(int year, int mon)
 {
     if (DateTime.isLeapYear(year))
     {
         return(DateTime.daysInMonLeap[mon]);
     }
     else
     {
         return(DateTime.daysInMon[mon]);
     }
 }