CDavGroupdavClientCalendar::getExDateShift

private function getExDateShift(string $startTime, $startTz, $excludeTz): int
{
	static $start;
	try
	{
		if (empty($start))
		{
			$tzFrom = new DateTimeZone($startTz);
			$start = new DateTime($startTime, $tzFrom);
		}

		$tzTo = new DateTimeZone($excludeTz);
		$startDateCode = $start->format('Ymd');
		$excludeDateCode = (clone $start)->setTimezone($tzTo)->format('Ymd');

		return $startDateCode <=> $excludeDateCode;
	}
	catch(Exception $e)
	{
	    return 0;
	}
}