Recommendation 2 of the 5th CCDS (1970)
Definition of TAI
International Atomic Time (TAI) is the time reference coordinate established by the Bureau International de l'Heure on the basis of the readings of atomic clocks operating in various establishments in accordance with the definition of the second, the unit of time of the International System of Units.
DOI : 10.59161/CCDS1970REC2E
The reader should note that the official version of this Resolution is the French text