CDavICalendarTimeZone::getTimeZoneId

static function getTimeZoneId($userId = null, $date = null)
{
	global $USER;
	$dateKey = $date ?? 0;
	$userIdKey = $userId ?? 0;
	if ($userId === null)
	{
		$userId = $USER->GetID();
	}

	static $timezoneCache = [];
	if (isset($timezoneCache[$userIdKey][$dateKey]))
	{
		return $timezoneCache[$userIdKey][$dateKey];
	}

	$autoTimeZone = $userZone = '';
	$factOffset = 0;

	if ($date === null)
	{
		$date = time();
	}

	static $userCache = [];

	if ($userId === null)
	{
		$autoTimeZone = trim($USER->GetParam("AUTO_TIME_ZONE"));
		$userZone = $USER->GetParam("TIME_ZONE");
	}
	else
	{
		if (!isset($userCache[$userId]))
		{
			$dbUser = CUser::GetList(
				"id",
				"asc",
				array("ID_EQUAL_EXACT" => (int)$userId),
				array("FIELDS" => array("AUTO_TIME_ZONE", "TIME_ZONE", "TIME_ZONE_OFFSET"))
			);
			if (($arUser = $dbUser->Fetch()))
			{
				$userCache[$userId] = array(
					"AUTO_TIME_ZONE" => trim($arUser["AUTO_TIME_ZONE"] ?? ''),
					"TIME_ZONE" => $arUser["TIME_ZONE"],
					"TIME_ZONE_OFFSET" => $arUser["TIME_ZONE_OFFSET"]
				);
			}
		}

		if (isset($userCache[$userId]))
		{
			$autoTimeZone = $userCache[$userId]["AUTO_TIME_ZONE"];
			$userZone = $userCache[$userId]["TIME_ZONE"];
			$factOffset = $userCache[$userId]["TIME_ZONE_OFFSET"];
		}
	}

	if (CTimeZone::IsAutoTimeZone($autoTimeZone))
	{
		static $userOffsetCache = array();

		if (!isset($userOffsetCache[$userId ?? 0]))
		{
			$userOffsetCache[$userIdKey] = CTimeZone::GetOffset($userId);
		}

		$userOffset = $userOffsetCache[$userIdKey];

		$localTime = new DateTime();
		$localOffset = $localTime->getOffset();

		$timezoneCache[$userIdKey][$dateKey] = self::getTimezoneByOffset($date, $userOffset + $localOffset);
	}
	else
	{
		if ($userZone && isset(self::$arTimeZones[$userZone]))
		{
			$timezoneCache[$userIdKey][$dateKey] = $userZone;
		}
		else
		{
			$localTime = new DateTime();
			$localOffset = $localTime->getOffset();

			$timezoneCache[$userIdKey][$dateKey] = self::getTimezoneByOffset($date, $factOffset + $localOffset);
		}
	}

	return $timezoneCache[$userIdKey][$dateKey];
}