International Atomic Time <time, standard> (TAI) An international standard measurement of time based on the comparison of many {atomic clocks}. TAI is maintained by the Bureau International des Poids et Mesures (BIPM), the world's governing body for civil atomic time measurement. TAI is the basis for {Coordinated Universal Time}. BIPM (http://bipm.fr/enus/5_Scientific/c_time/time_1.html). (2001-08-02)