Click on any of the "hour squares" in the Clear Sky Clock above to see an explanation of all its terms and symbols.

The U.S. Naval Observatory clock below does not run in Microsoft Internet Explorer. It does run for a maximum of 30 seconds in other browsers such as Netscape Navigator and Mozilla Firefox. "Refresh" or "Reload" your browser (usually by pressing your F5 key) to re-activate the clock for a few seconds.

For a continuously operating real-time clock showing areas of the Earth in daylight and darkness visible in all browsers click

here