This article explains how the National Institute of Standards and Technology (NIST) maintains accurate time standards, which are essential for global timekeeping. NIST-F1, a highly precise cesium fountain clock, serves as the U.S. primary frequency standard, with an uncertainty of less than 1 part in 10¹⁵. NIST uses a real-time time scale called AT1, which combines data from multiple atomic clocks to keep time as stable as possible. UTC(NIST), the U.S. version of Coordinated Universal Time, is based on AT1 but is adjusted periodically to align with the global UTC standard, using data from the International Bureau of Weights and Measures (BIPM).
The article also provides a table with specific parameters used to calculate the difference between UTC(NIST) and AT1 at any given time. These parameters include leap seconds, time offsets, and frequency adjustments. The values change monthly, with updates typically made at the start of each month. This system ensures that time measurements remain accurate and consistent, supporting applications like telecommunications, navigation, and scientific research.
Keywords: frequency standard, atomic time scale, UTC(NIST)
