Get a DateTime object based on a random date between a given date and 1
        second ago.
        Accepts date strings that can be recognized by strtotime().

        :param start_date Defaults to "-30d"
        :param tzinfo: timezone, instance of datetime.tzinfo subclass
        :example DateTime('1999-02-02 11:42:52')
        :return DateTime

def past_datetime(self, start_date='-30d', tzinfo=None):
        """
        Get a DateTime object based on a random date between a given date and 1
        second ago.
        Accepts date strings that can be recognized by strtotime().

        :param start_date Defaults to "-30d"
        :param tzinfo: timezone, instance of datetime.tzinfo subclass
        :example DateTime('1999-02-02 11:42:52')
        :return DateTime
        """
        return self.date_time_between(
            start_date=start_date, end_date='-1s', tzinfo=tzinfo,
        )