QDateTime::fromString doesn't accept Time Zone Designator, even with Qt::ISODate as date format

QDateTime::fromString( str, Qt::ISODate ) seems not to be ISO8601 compatible. If I use time zone designator then QDateTime has invalid value (time is 00:00:00), however it returns that it's valid.
Try please these few lines:
//
QDateTime time = QDateTime::fromString( "1987-02-13T13:24:51+01:00", Qt::ISODate );
bool isValid = time.isValid(); //isValid == true ???
QString str = time.toString(); //"Fri Feb 13 00:00:00 1987" ???