NIST has officially launched NIST-F2
More Info: http://go.usa.gov/kqbQ.

NIST-F2, a new atomic clock based on a "fountain" of cesium atoms, is now the U.S. civilian time standard. NIST-F2 will neither gain nor lose one second in 300 million years, making it more than twice as accurate as its predecessor, NIST-F1, which was the U.S. civilian time and frequency standard since 1999.