def getBounds(self, tzinfo=None):
        if self.resolution >= datetime.timedelta(days=1) \
        and tzinfo is not None:
            time = self._time.replace(tzinfo=tzinfo)
        else:
            time = self._time
        return (
            min(self.fromDatetime(time), self.fromDatetime(self._time)),
            max(self.fromDatetime(time + self.resolution),
                self.fromDatetime(self._time + self.resolution))
        )