Hi Brendan, Hit menu, then Navi set up, then Cailbration, then clock set. There you can change the hour only, the system will only set the minutes automaticly.
Also - make sure you're NavData is set to the region you are in. I had to do that when I first got mine. You'll see a map of the USA and you can change the predetermined regions. I do not recall off the top of my head how to get to that screen. I am NOT sure if that has ANYTHING to do with the clock & time zones.