We updated to 4.4 on early Monday morning, and immediately took advantage of the scheduled charging feature (yay!), setting up the charge for 9:15pm (Pacific Time). Later that day, I flew to Chicago... As I was waiting for a cab from the airport, I took a quick peek at the app. It said that the charging was scheduled for 11:15pm. That caught me offguard, and then I realized it was displaying in local time. Nice! Not a big thing, but I thought it was a nice touch.
yes, i believe the entire car's system uses UTC and converts to local based on your gps. as does iOS. a good thing and the right way to do it.
As an aside, it would be nice to enable and set the scheduled charge time from the app. I believe you can only do this in the car.