OutgoingEventManager::getInstanceByOriginalDate

private function getInstanceByOriginalDate(SyncEvent $masterEvent, $event): ?SyncEvent
{
	if (isset($event['originalStartTime']['dateTime']))
	{
		$eventOriginalStart = Date::createDateTimeFromFormat(
			$event['originalStartTime']['dateTime'],
			DateTimeInterface::ATOM
		);
	}
	elseif (isset($event['originalStartTime']['date']))
	{
		$eventOriginalStart = Date::createDateFromFormat(
			$event['originalStartTime']['date'],
			Helper::DATE_FORMAT
		);
	}

	return $masterEvent
		->getInstanceMap()
		->getItem(InstanceMap::getKeyByDate($eventOriginalStart));
}