Way to set date so GPS doesn't use wrong time?

I have a issue with the GPS. I live in AZ and drove to Cali this last week. My car time changed to west coast time when it should have stayed the same.
We (AZ) are on west coast time now until fall when we go to Mountain time. Anyway, I look at my settings and it's set to AZ timezone. So my first thought is that the car has a date clock that is incorrect and needs to be adjusted.
Well I can't seem to find it and haven't had the time to pull out the manual. I'm traveling a lot this summer for work. Any clues?

Thanks