I just got back from a road trip in my '07 ML320. I was a little surprised that the nav system didn't auto change the clock when I crossed into a new time zone (I know the Honda/Acura system does). Am I missing a setting or does the MB system not do this?

 

It does not do this automatically. You need to change it manually, which I think can be done by hitting the SERV button, then hitting Time.