PHP Send outlook event by ical ปัญหาเวลาไม่ตรงกับการส่ง

$calendar = new Calendar();
$calendar
    ->addTimeZone(TimeZone::createFromPhpDateTimeZone(new PhpDateTimeZone('Asia/Bangkok')))
    ->addTimeZone(TimeZone::createFromPhpDateTimeZone(new PhpDateTimeZone('Europe/London')))
;

$timezone = new \DateTimeZone('Asia/Bangkok');
$event = new \Sabre\VObject\Component\VCalendar();
$event->add('DTSTART', $timezone->getDateTime());
$event->add('DTEND', $timezone->getDateTime());
$event->add('TZID', 'Asia/Bangkok');

$event->save('event.ics');