NIST-F2, an atomic clock launched in 2014 to help keep official U.S. time, would neither gain nor lose one second in about 300 million years.

NIST-F2, launched in 2014 as a U.S. civilian time standard, would neither gain nor lose one second in about 300 million years.

The National Institute of Standards and Technology officially launched NIST-F2 on April 3, 2014, in Boulder, Colorado, to serve as a new U.S. civilian time and frequency standard alongside NIST-F1.

NIST said the new clock would neither gain nor lose one second in about 300 million years, about three times as accurate as NIST-F1, the standard since 1999. Both are cesium fountain clocks, using a 'fountain' of cesium atoms to determine the exact length of a second.