It seems that calendars should respond to time zone changes more gracefully.
I don't have another smartphone for reference, just an iPhone, but the combination of automatic time zone updating and calendar appointments should be handled more gracefully.
Now, I know there's a time zone support option on the iPhone, but not all appointment sources are created equal.
Outlook Sync with iphone seems to not handle timezones well. I'm sitting in Las Vegas getting my 4 PM EST meeting invite reminders at 4 PM PST.
Meanwhile, I wouldn't necessarily want my 5:30 AM EST to necessarily translate to 2:30 AM PST.
Given those two cases, I don't think a global device setting is necessarily the ideal method to solve the timezone issue.
Maybe there should be switch on each appointment that indicates whether the time or the timezone stays fixed for a given appointment.