Currently you can only convert a QDateTime (or the QDate and QTime objects for that matter) object to local time or UTC. And thereby calculate the offset on the current system. There is no support for creating a QDateTime object from a string with time zone information, there is no way to get the time zone information back again. Also you can't convert between a textual representation of a time zone (say CET) and its offset (+0100).
Therefore I kindly request to add real time zone support like it is offered by the KDE libraries (e.g. through the KDateTime and KTimeZone/[KTimeZones|http://api.kde.org/4.x-api/kdelibs-apidocs/kdecore/html/classKTimeZones.html] classes). The most important parts are already available in QTopia/[Qt Extended|http://doc.trolltech.com/qtextended4.4/qtimezone.html].