WorldClock allows you to manage multiple clocks, for any country or timezone in the world! The powerful searchable offline engine allows you to add new timezones even when you don't have an internet connection (such as on a plane), while the Auto-Locate feature lets you add a new clock for your current location with the simple press of a button. The handy Timezone Calculator also helps you figure out those "if it is 6PM in Paris, what time will it be here" questions. Now with 24-hour support!

WorldClock screenshots: