code: def value_to_db(self, value):
          
          assert isinstance(value, datetime.date)
          assert not isinstance(value, datetime.datetime)
  
          try:
              value = value - datetime.date(year=1970, month=1, day=1)
          except OverflowError:
              raise tldap.exceptions.ValidationError("is too big a date")
  
          return str(value.days).encode("utf_8")
docs: Returns field's single value prepared for saving into a database.