def _month_converter(self, date_time):
        """Returns Billing API format YYYY-DD"""
        if not date_time:
            date_time = datetime.datetime.utcnow()
        if isinstance(date_time, datetime.datetime):
            date_time = '%s-%02d' % (date_time.year, date_time.month)
        return date_time
Returns Billing API format YYYY-DD