Being based in Italy, I have to deal with the fact that stuff happens in the US and I'm in a different time zone. I stay up late at night, and news keep coming in. Also, I have to consider time zone differences when setting up online meetings with developers, writers and casual contacts. Up until today, I used a neat web app called Every Time Zone which comes with an iPad-specific viewport and allows me to quickly check on various time zones worldwide.
Filopanti, however, might be a simpler solution I can fire up at any time to quickly check on U.S. time zone --namely San Francisco's time. With a straightforward and elegant UI Filopanti lets you pick two different cities and compare their time zones.
In the app, you choose two cities and you hit "Done". After that, you'll be presented the current time in the first city and the different timezone in the second one. You can adjust time with your fingers to a different time of the day or jump back to "Now" with the tap of a button. That's it.