The Official Time

	This public service is cooperatively provided by the two time agencies of the United States: a Department of Commerce agency, the National Institute of Standards and Technology (NIST), and its military counterpart, the U. S. Naval Observatory (USNO). Readings from the clocks of these agencies contribute to world time, called Coordinated Universal Time (UTC). The time maintained by both agencies should never differ by more than 0.000 0001 seconds from UTC (see recent comparisons).
	Go to: Time & Frequency Division, NIST Time Service Department, USNO

A Walk through Time History of timekeeping from ancient to modern times. (at NIST) Calendars through the Ages Systems of counting the days, months, and years. (at webexhibits.org) Daylight Saving Time When and why do we change our clocks? (at webexhibits.org) ClockWorks Illustrated mechanisms of many historical clocks. (at Britannica) It's About Time Advances in timekeeping accuracy and atomic clocks. (at University of Wisconsin) The Quartz Watch What's inside your wristwatch? See stories and timeline. (at Smithsonian) Disclaimer Note: Linking to these sites does not imply recommendation or endorsement of the information or commercial products by NIST or USNO.