Hello! My name is Don. I am a program coordinator at the Philadelphia Education Fund. This is my first attempt at researching a topic on the web and synthesizing all the possibilities into a coherent format. Let me start from a personal point of interest...

When I lived in Boulder Colorado I was always excited to be able to call the Atomic Clock at (303) 499-7111. In fact, I had it on auto-dial on my phone. Of course you could call the Atomic clock too, but it might be a toll call. Fortunately, you can visit this clock and many more important clocks on the World Wide Web.

A good place to start on a web research journey on the subject of clocks and time is the web version of the short book A Walk Through Time which was written by staff of the National Institute for Standards and Technology (NIST). This elementary history of time and frequency traces the development of time keeping in relationship to human needs and technology from the earliest celestial-based calendars through the atomic clock whose time and frequency signals are relayed through global positioning satellites within one millionth of a second of Universal Coordinated Time.

Any research into clocks on the web brings you again and again to two agencies. The first is the National Institute of Standards and Technology (NIST) in Boulder, Colorado which houses the atomic clock and is responsible for maintaining the U.S. national frequency standards. Visit for a history with supporting links. A web version of the Atomic Clock is also on-line. From there you can synchronize your computer clock.

The second agency is the U.S. Naval Observatory's Time Service Department in Washington D.C. which maintains the official time for the United States. A page at this site allows you to figure out how to compute your own apparent local sidereal time using your longitude, latitude, and UTC time. The USNO master clock and other clocks on the web can be found at this site.

Another agency which has a hand in the control of time is the International Bureau of Weights and Measures in Paris. This agency is responsible for coordinating Universal Coordinated Time (UTC) and the designation of leap seconds. You'll find a diagram of the international integration of time on an affiliated agency's website from Japan.

Other interesting spots to visit:

Visit the web representation of the prime meridian home of Greenwich Mean Time (GMT). Check out the over-the-top promotion for the new Greenwich 2000 Dome. (Don't forget to turn off the frames which will make all the distracting banners go away.)

Here is a nice index of directories for clocks and time on horologist Gordon Uber's own website.

Enjoy!