def _parse_api_time(timestr):
        """
        Typical expiration times returned from the auth server are in this
        format:
            2012-05-02T14:27:40.000-05:00
        They can also be returned as a UTC value in this format:
            2012-05-02T14:27:40.000Z
        This method returns a proper datetime object from either of these
        formats.
        """
        try:
            reg_groups = API_DATE_PATTERN.match(timestr).groups()
            yr, mth, dy, hr, mn, sc, off_sign, off_hr, off_mn = reg_groups
        except AttributeError:
            # UTC dates don't show offsets.
            utc_groups = UTC_API_DATE_PATTERN.match(timestr).groups()
            yr, mth, dy, hr, mn, sc = utc_groups
            off_sign = "+"
            off_hr = off_mn = 0
        base_dt = datetime.datetime(int(yr), int(mth), int(dy), int(hr),
                int(mn), int(sc))
        delta = datetime.timedelta(hours=int(off_hr), minutes=int(off_mn))
        if off_sign == "+":
            # Time is greater than UTC
            ret = base_dt - delta
        else:
            ret = base_dt + delta
        return ret