The event's start time, as a timezone-aware datetime object

def start(self):
        """The event's start time, as a timezone-aware datetime object"""
        if self.start_time is None:
            time = datetime.time(hour=19, tzinfo=CET)
        else:
            time = self.start_time.replace(tzinfo=CET)
        return datetime.datetime.combine(self.date, time)