The BIPM and the accurate measurement of time

The role of the Bureau International des Poids et Mesures (BIPM) in assuring the uniformity and reliability of the world´s measurement system is described. A brief discussion follows on the meaning of the term accurate measurement. The development of atomic time scales is outlined with particular reference to the Bureau International de l´Heure and the origins of International Atomic Time (TAI) and Coordinated Universal Time (UTC). The author ends with a brief description of the work currently being carried out at the BIPM, which includes the regular establishment of TAI, its diffusion with UTC, and the associated research work aimed at improving these scales and their accessibility