To find out the official time, visit the joint Web site of the National Institute of

Standards and Technology and the U.S. Naval Observatory. Two

ultraprecise clocks contribute to a pool used to define “coordinated universal

time.” These two clocks are not supposed to differ by more than one

ten-millionth of a second. The site also provides links to presentations on

topics such as timekeeping, calendars, and clocks.

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From the Nature Index

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