public static function toDateTimeString(
        AdManagerDateTime $adManagerDateTime,
        $timeZoneId = null
    ) {
        $dateTime = self::toDateTime($adManagerDateTime);
        if ($timeZoneId !== null) {
            $dateTime->setTimezone(new DateTimeZone($timeZoneId));
        }

        return $dateTime->format(DateTime::ATOM);
    }