I don't believe you 'set' a GMT watch. just turn the bezel to whatever timezone you want. this way, the dial tells you your lacal time, the bezel the timezone you want.

: Hello all,
: I found this site through a web search and
: recently bookmarked it due to my two new
: Tag's. I do have a question if anyone would
: be so kind...How do you set the GMT
: function? I bought the watch without a
: manual. Any help would be great, I've
: enclosed a link for the watch.
: Thanks in advance,
: Bob