docs: def to_dt(date, default_tz=None):
      """
      Returns a non-naive datetime.datetime.
  
      Interprets numbers as ms-since-epoch.
  
      Parameters
      ----------
      date : `int` or `datetime.datetime`
          The datetime to convert
  
      default_tz : tzinfo
          The TimeZone to use if none is found.  If not supplied, and the
          datetime doesn't have a timezone, then we raise ValueError
  
      Returns
      -------
      Non-naive datetime
      """
      if isinstance(date, (int, long)):
          return ms_to_datetime(date, default_tz)
      elif date.tzinfo is None:
          if default_tz is None:
              raise ValueError("Must specify a TimeZone on incoming data")
          return date.replace(tzinfo=default_tz)
      return date