CCalendarEvent::convertRuleUntilToInternalFormat

static function convertRuleUntilToInternalFormat(?string $untilString): ?string
{
	if (!empty($untilString) && preg_match('/UNTIL=(.+)[;$]/U', $untilString, $matches))
	{
		$internalFormatedDate = self::convertDateToRecurrenceFormat($matches[1]);
		$untilString = str_replace($matches[1], $internalFormatedDate, $untilString);
	}

	return $untilString;
}