src/TimeZoneRegion.php
public static function getAllIdentifiers(bool $includeObsolete = false) : array
    {
        return \DateTimeZone::listIdentifiers(
            $includeObsolete
            ? \DateTimeZone::ALL_WITH_BC
            : \DateTimeZone::ALL
        );
    }
public static function getAllIdentifiers(bool $includeObsolete = false) : array
    {
        return \DateTimeZone::listIdentifiers(
            $includeObsolete
            ? \DateTimeZone::ALL_WITH_BC
            : \DateTimeZone::ALL
        );
    }
public static function getAllIdentifiers ( bool $ includeObsolete = false ) : array { return \ DateTimeZone :: listIdentifiers ( $ includeObsolete ? \ DateTimeZone :: ALL_WITH_BC : \ DateTimeZone :: ALL ) ; }
Returns all the available time-zone identifiers.

@param bool $includeObsolete Whether to include obsolete time-zone identifiers. Defaults to false.

@return string[] An array of time-zone identifiers.
Returns all the available time - zone identifiers .