Seconds since the Unix epoch (January 1 1970 00:00:00 GMT)

def U(self):
    "Seconds since the Unix epoch (January 1 1970 00:00:00 GMT)"
    if getattr(self.data, 'tzinfo', None):
      return int(calendar.timegm(self.data.utctimetuple()))
    else:
      return int(time.mktime(self.data.timetuple()))