def _format_strings(self):
values = self.values.astype(object)<EOL>is_dates_only = _is_dates_only(values)<EOL>formatter = (self.formatter or<EOL>_get_format_datetime64(is_dates_only,<EOL>date_format=self.date_format))<EOL>fmt_values = [formatter(x) for x in values]<EOL>return fmt_values<EOL>
we by definition have a TZ