CCalendar::GetTimezoneOffset

static function GetTimezoneOffset($timezoneId, $dateTimestamp = false)
{
	$offset = 0;
	if ($timezoneId)
	{
		try
		{
			$oTz = new DateTimeZone($timezoneId);
			if ($oTz)
			{
				$offset = $oTz->getOffset(new DateTime($dateTimestamp ? "@$dateTimestamp" : "now", $oTz));
			}
		}
		catch(Exception $e){}
	}
	return $offset;
}