def _format_strings(self):

        values = self.values
        if not isinstance(values, DatetimeIndex):
            values = DatetimeIndex(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()
we by definition have DO NOT have a TZ
dataset/ETHPy150Open pydata/pandas/pandas/formats/format.py/Datetime64Formatter._format_strings