'Return the timestamp of the most recent data.'

@property
def last_update(self):

    (date, time) = (self.data.get('update_date'), self.data.get('update_time'))
    if ((date is not None) and (time is not None)):
        return datetime.strptime((date + time), '%d-%m-%Y%H:%M').replace(tzinfo=pytz.timezone('Europe/Vienna'))
