Atomic clock accuracy needed

The National Institute of Standards and Technology (NIST), formerly The National Bureau of Standards, has been working with atomic clocks for over forty years. They have come a long way since they developed the world's first atomic clock. NIST has also introduced NIST-7, one of the most accurate clocks to date and is expected, after full evaluation, to show an accuracy of one part in 10/sup 14/, equivalent to one second in three million years. Atomic clocks are based on natural resonances in atoms, which involve highly stable and periodic events at very high frequencies.>