Create a new DateRange with the datetimes converted to dates and changing to CLOSED/CLOSED.

def as_dates(self):
        """
        Create a new DateRange with the datetimes converted to dates and changing to CLOSED/CLOSED.
        """
        new_start = self.start.date() if self.start and isinstance(self.start, datetime.datetime) else self.start
        new_end = self.end.date() if self.end and isinstance(self.end, datetime.datetime) else self.end
        return DateRange(new_start, new_end, CLOSED_CLOSED)