we by definition have DO NOT have a TZ

def _format_strings(self):
        """ we by definition have DO NOT have a TZ """

        values = self.values

        if not isinstance(values, DatetimeIndex):
            values = DatetimeIndex(values)

        if self.formatter is not None and callable(self.formatter):
            return [self.formatter(x) for x in values]

        fmt_values = format_array_from_datetime(
            values.asi8.ravel(),
            format=_get_format_datetime64_from_values(values,
                                                      self.date_format),
            na_rep=self.nat_rep).reshape(values.shape)
        return fmt_values.tolist()