International "We are Open/Closed" Message

Hi all,

I would like to display a message in flash “we are open” or “we are closed” based upon time. Naturally I can do this for the users local time on their system, but is it possible to work out if their time is different to UK time (GMT) and display those messages accordingly. Afterall I don’t want a user to see a message “we are open” at 1pm their time - they could be in Japan and it’d be about 4am UK time.

Is this possible to work out the time difference on any system?