Discover when and where people observe Daylight Saving Time and Summer Time, and when you should switch your clocks.

Generally speaking, countries in higher latitudes have Daylight Saving Time, and countries near the equator do not. Explore the variety by twirling the globe, and tapping on countries. Or type in a country name. You’ll learn whether or not that country observes Daylight Saving Time, and if so, what date and time it will start or end during any given year.

Share the dates! You can remind others to spring ahead or fall back thanks to the app’s full integration with email, Facebook, and Twitter.

In addition, the app explores the rationale behind Daylight Saving Time, its history, and its unintended consequences. Does having more daylight in the evening really save energy? How can Daylight Saving Time switch the birth order of twins? How did Daylight Saving Time thwart would-be terrorist bombers?