World Time Buddy

I think it's the best for seeing multiple time zones! :)

I always keep two additional timezones displayed in the clock widget on my phone's home screen ,showing SF (-9h) and Seoul (+7h) time. It's easy to guesstimate anything between and beyond from that on. Sure it's not sufficient enough for scheduling, but a first dirty little helper.

I SWEAR by this app: I work with people in several different time zones, and World Time Buddy is perfect for making sure I'm not scheduling a Skype call for 3:00 am in someone's local time

+1 from me!