An illustrated history of timekeeping from ancient times to the present.

Calculate the exact time in days, hours, minutes and seconds from now until your birthday or any other event.

Why do we use daylight savings time and who invented it?

International Standard ISO 8601 specifies numeric representations of date and time. It helps to avoid confusion caused by the many different national notations.

Introduction to latitude and longitude, a way of calculating exactly where you are anyplace on earth and a way to tell time.

Find out what time it is anywhere in the world.

Learn how to tell time by finding constellations in the night sky.

Learn how to make a sundial. Instructions are for beginners, intermediate, or advanced, and work for either the northern or southern hemispheres.

Before there were clocks, people used shadows to tell time. Learn how to make your own sun clock!

Benjamin Franklin first called for the government to tinker with clock hours in the 1780s. But it wasn't until World War I that the United States adopted daylight-saving time as a way to get more efficiency out of the day. "Seize the Daylight" Author David Prerau talks about the complicated politics and curious history of DST, and he shares an excerpt from his book. [4:54 streaming audio broadcast]

Just how do we measure time and what has Greenwich England got to do with it?

Is time travel possible? See what Carl Sagan and Einstein had to say about time travel in this NOVA special.

Gives the current time, synchronized by NIST. Close to 100 different time zones supported, as well as the ability to select the default time zone.

Provides online times converter and brief information about GMT/UTC.