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Time Realization

Time and Frequency Realization

Coordinated Universal Time, abbreviated as UTC, is the official, internationally agreed upon standard for world time. NIST’s own representation of UTC, called UTC(NIST), serves as the official time and frequency standard for the United States. UTC(NIST) consists of a large group of continuously running atomic clocks, whose outputs are combined with weighted average techniques to form a single clock. UTC(NIST) agrees with UTC to within a few nanoseconds, and its frequency is periodically calibrated with state-of-the-art primary microwave and optical frequency standards that were designed and built by NIST.

Created October 7, 2020, Updated May 22, 2023