1         public static int DateDiffDay(DateTime DateTimeOld, DateTime DateTimeNew)
 2         {
 3             TimeSpan ts1 = new TimeSpan(DateTimeOld.Ticks);
 4             TimeSpan ts2 = new TimeSpan(DateTimeNew.Ticks);
 5             TimeSpan ts = ts1.Subtract(ts2).Duration();
 6             int day = ts.Days;
 7             if (day < -3)
 8                 return -1;
 9             else if (day == 0)
10                 return 1;
11             else return 0;
12         }