QTimeZone::isTimeZoneIdAvailable is giving wrong result.

#include <QDateTime>
#include <QTimeZone>
#include <QDebug>

int main()
{
    QTimeZone tzFromId("UTC+01");

    qDebug() << "This is true:" << tzFromId.isValid();
    qDebug() << "This is UTC+01:" << QTimeZone(60*60).id();
    qDebug() << "So this should be true, but is false:"
             << QTimeZone::isTimeZoneIdAvailable(tzFromId.id());

    return 0;
}