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International Atomic Time (TAI)

In 1967, the Thirteenth General Conference of Weights and Measures adopted a resolution to replace the astronomical definition of the second - the second is the duration of 9,192,631,770 cycles of radiation corresponding to the transition between two hyperfine levels of the ground state of Caesium-133 atom.  The International Atomic Time (TAI) is the international reference scale of atomic time based on the seconds as defined above in the International System of Units (SI).

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It is in the form of a continuous scale, i.e. in days, hours, minutes and seconds from the origin 1958 January 1 d 0 h 0 min 0 s.  The atomic time scale is accurate to a few billionths of a second as compared to a few thousandths of a second per day in Universal Time.

Last revision date: <20 Dec 2012>