Over at The Sweet Setup, Zones was chosen as the best time zone calculator for iPhone. It was chosen for its simple UI, minimal functionality, and ability to look at specific future times in many time zones. If you work with others who are on different time zones, Zones is a must have app for your iPhone.
At just $.99, Zones is an affordable way to know if your co-workers across the pond are asleep, still working, or out to dinner. Be sure to read the entire review to see the details of why it was chosen along with the other options.