UTC is the international atomic time scale that serves as the basis of timekeeping for most of the world. The hours, minutes, and seconds expressed by UTC represent the time of day at the Prime Meridian (0º longitude) located near Greenwich, England as reckoned from midnight. UTC is calculated by the Bureau International des Poids et Measures (BIPM) in Sevres, France. The BIPM averages data collected from more than 200 atomic time and frequency standards located at about 50 laboratories worldwide. UTC is the basis for all civil time, with the world divided into time zones expressed as positive or negative differences from UTC. UTC is also referred to as "Zulu time." See the Standard Time Zones of the World map included with the Reference Maps.