International Atomic Time
Quick Summary
International Atomic Time (TAI) is a highly accurate timescale generated by a network of atomic clocks worldwide. Unlike previous methods that relied on Earth's rotation and orbit, atomic clocks use the precise frequencies of atomic transitions to measure time.12
TAI is formed by averaging signals from approximately 270 laboratory atomic clocks and is maintained by the International Bureau of Weights and Measures. Since 1972, TAI has been adjusted with leap seconds to create Coordinated Universal Time (UTC), the global standard that aligns atomic time with Earth's actual rotation. Modern cesium fountain clocks are so accurate they are expected to be off by less than a second in over 50 million years.1
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