New U.S. time standard Atomic clock will neither gain nor lose one second in about 300 million years

National Institute of Standards and Technology has officially launched a new atomic clock, called NIST-F2, to serve as a new US civilian time and frequency standard, along with the current NIST-F1 standard. NIST-F2 would neither gain nor lose one second in about 300 million years, making it about three times as accurate as NIST-F1, which has served as the standard since 1999. Both clocks use a 'fountain' of cesium atoms to determine the exact length of a second.