def as_iso8601(self, include_millis=False):
        """
        example: 2016-08-13T00:38:05.210+01:00
        """
        date = self.__datetime.strftime("%Y-%m-%d")
        time = self.__datetime.strftime("%H:%M:%S")

        # millis...
        if include_millis:
            micros = float(self.__datetime.strftime("%f"))
            millis = ".%03d" % (micros // 1000)

        else:
            millis = ""

        # time zone...
        zone = self.__datetime.strftime("%z")

        # Z format...
        if float(zone[1:]) == 0.0:
            return "%sT%s%sZ" % (date, time, millis)

        # numeric format...
        zone_hours = zone[:3]
        zone_mins = zone[3:]

        return "%sT%s%s%s:%s" % (date, time, millis, zone_hours, zone_mins)
example: 2016-08-13T00:38:05.210+01:00