Your appointments don't change.  They stay at the absolute time at which you
set them.  The PC's clock changed, not Outlook.  If you entered an all-day
appointment in, say, the Central time zone, then changing your time zone in
Windows to, say, Mountain time, the original all-day appointment will now
run from 11 PM one day to 11 PM the next because it's still an Eastern time
zone event.

Don't change the time zone of the PC.  Use Outlook's alternate time zone
feature.  Tools>Options>Calendar Options>Time Zone>Show an additional time
zone.