code: def CalcDayOfWeek(self):
          
          # rip apart the value
          year, month, day, day_of_week = self.value
  
          # assume the worst
          day_of_week = 255
  
          # check for special values
          if year == 255:
              pass
          elif month in _special_mon_inv:
              pass
          elif day in _special_day_inv:
              pass
          else:
              try:
                  today = time.mktime( (year + 1900, month, day, 0, 0, 0, 0, 0, -1) )
                  day_of_week = time.gmtime(today)[6] + 1
              except OverflowError:
                  pass
  
          # put it back together
          self.value = (year, month, day, day_of_week)
docs: Calculate the correct day of the week.