I don't have this model. But, this thread - GRAND CARRERA GMT - setting the 2nd time zone. > https://www.watchuseek.com/f25/grand-carrera-gmt-setting-2nd-time-zone-467104.html , might help.

Also, see - Tag Heuer Carrera Calibre 8 GMT > Tag Heuer | Watching LAJ

 

Yeah i found similar problem. But finally manage to figure it out. You have to move the hour hand backward for 15 minutes from the current time. And then you will be able to change the gmt. Unfortunately it cannot be adjusted separately.

 

Hey guys. I could not find anything on the calibre i GMT. I am trying to change the GMT within the watch but i cant see to figure it out. Please advise on how to change that time. Thanks. Greatly appreciated. [iurl="https://www.watchuseek.com/attachment.php?attachmentid=1583019&d=1406938569"]

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Pull the crown turn crown anti clock wise - GMT small display hour Hand will get stuck at 1 - adjust by going back to 1 on the original. Once set at desired time it will change automatically.