Parse a date into canonical format of datetime.dateime.

        :param my_date:    Either datetime.datetime or string in 
                           '%Y-%m-%dT%H:%M:%SZ' format.

        ~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-

        :return:  A datetime.datetime.

        ~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-

        PURPOSE:  Parse a date and make sure it has no time zone.

def parse_date(my_date):
        """Parse a date into canonical format of datetime.dateime.

        :param my_date:    Either datetime.datetime or string in 
                           '%Y-%m-%dT%H:%M:%SZ' format.

        ~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-

        :return:  A datetime.datetime.

        ~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-

        PURPOSE:  Parse a date and make sure it has no time zone.

        """
        if isinstance(my_date, datetime.datetime):
            result = my_date
        elif isinstance(my_date, str):
            result = datetime.datetime.strptime(my_date, '%Y-%m-%dT%H:%M:%SZ')
        else:
            raise ValueError('Unexpected date format for "%s" of type "%s"' % (
                str(my_date), type(my_date)))
        assert result.tzinfo is None, 'Unexpected tzinfo for date %s' % (
            result)
        return result