For international travelers who cross many times zones each day, such as those in aviation and those in the military, it is common to live by Coordinated Universal Time (also known as UTC, Z or Zulu, and GMT or Greenwich Mean Time). An earlier hint noted that the iPhone can display UTC in the World Clock, but you can also set your iPhone to stay on UTC.
To change to UTC you must first select Settings > General > Date & Time. Turn off Set Automatically. You should also turn on 24-Hour Time, which is optional but is most likely used by anyone who needs to live by UTC. When you turn off Set Automatically, you are shown the Time Zone option. Select Time Zone and type in UTC in the search box. Select UTC from results list. The iPhone will now stay on UTC regardless of your location in the world.
[kirkmc adds: No iPhone here, but on the iPod touch you can set the time zone to UTC if you want.]
Mac OS X Hints
http://hints.macworld.com/article.php?story=20080811134801975