SqlDateTime overflow. Must be between 1/1/1753 12:00:00 AM and 12/31/9999 11:59:59 PM.

protected void FillBookingDataset()
       {
           DateTime firstDate = new DateTime(ASPxCalendar1.VisibleDate.Year,
        ASPxCalendar1.VisibleDate.Month, 1);
           DateTime lastDate = GetFirstDayOfNextMonth();
           dsBooking = GetCurrentMonthData(firstDate, lastDate);
       }

       protected DateTime GetFirstDayOfNextMonth()
       {
           int monthNumber, yearNumber;
           if (ASPxCalendar1.VisibleDate.Month == 12)
           {
               monthNumber = 1;
               yearNumber = ASPxCalendar1.VisibleDate.Year + 1;
           }
           else
           {
               monthNumber = ASPxCalendar1.VisibleDate.Month + 1;
               yearNumber = ASPxCalendar1.VisibleDate.Year;
           }