NIST-F1

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NIST-F1, source of the official time of the United States
NIST-F1, source of the official time of the United States

NIST-F1 is a cesium fountain atomic clock that serves as the United States' primary time and frequency standard. As of the summer of 2005, it is so accurate that it will neither gain nor lose one second in more than 60 million years. The clock took less than four years to test and build, and was developed by Steve Jefferts and Dawn Meekhof of the National Institute of Standards and Technology (NIST) physics lab in Boulder, Colorado.

The clock replaces NIST-7, a cesium beam atomic clock used from 1993 to 1999. NIST-F1 is approximately 10 times more accurate than NIST-7.

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