docs: def format_date(value, format='%b %d, %Y', convert_tz=None):
      """
      Format an Excel date or date string, returning a formatted date.
      To return a Python :py:class:`datetime.datetime` object, pass ``None``
      as a ``format`` argument.
  
      >>> format_date(42419.82163)
      'Feb. 19, 2016'
  
      .. code-block:: html+jinja
  
          {{ row.date|format_date('%Y-%m-%d') }}
      """
      if isinstance(value, float) or isinstance(value, int):
          seconds = (value - 25569) * 86400.0
          parsed = datetime.datetime.utcfromtimestamp(seconds)
      else:
          parsed = dateutil.parser.parse(value)
      if convert_tz:
          local_zone = dateutil.tz.gettz(convert_tz)
          parsed = parsed.astimezone(tz=local_zone)
  
      if format:
          return parsed.strftime(format)
      else:
          return parsed