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Physical Measurement Laboratory /Time and Frequency Division

Time Realization and Distribution

The Time Realization and Distribution group distributes standard time and frequency signals generated by the Coordinated Universal Time scale, UTC(NIST), maintained at the NIST laboratories in Boulder, Colorado. UTC(NIST) is the U. S. national standard for time-of-day, time interval, and frequency.

NIST-F1 Cesium Fountain Atomic Clock
NIST-F1 Atomic Clock
time scales
UTC(NIST) Time Scale
Internet Time Service
Internet Time Service (ITS)
WWV building

WWV
Image of WWVB radio antennas

WWVB
WWVH entrance

WWVH

UTC(NIST) is freely distributed to many millions of users through radio, Internet, and telephone links. The services that distribute UTC(NIST) include shortwave radio stations WWV and WWVH, low frequency radio station WWVB, the Internet Time Service (ITS), the Automated Computer Time Service (ACTS), the telephone time service, and the web clock (time.gov). These services synchronize hundreds of millions of clock every day.

UTC(NIST) is also distributed through remote calibration services to paying customers who need the highest levels of accuracy. The demanding measurement needs of these customers are met through the Frequency Measurement and Analysis Service (FMAS) and the Time Measurement and Analysis Service (TMAS).

NBS/NIST Radio Stations: The Story of an Old Timer

NBS/DOC

This series of webpages will lead you on a journey on the history of the NBS/NIST radio stations. You can watch a video as well.

News and Updates

Projects and Programs

Publications

A Century of WWV: 100th Anniversary Commemoration

Author(s)
Glenn K. Nelson
WWV was established as a radio station on October 1, 1919 with the issuance of the call letters by the U.S. Department of Commerce. This paper will observe the

SIM Time Scale: 10 years of operation

Author(s)
J. M. Lopez, Michael A. Lombardi, E. de Carlos, N. Munoz, C. Ortiz
The Inter-American Metrology System (SIM) is one of the world's five major Regional Metrology Organizations (RMO's). Starting in 2005, the SIM Time and

Improving packet synchronization in an NTP server

Author(s)
Andrew N. Novick, Michael A. Lombardi, Kevin Franzen, John Clark
A computer or dedicated client can use the Network Time Protocol (NTP) to synchronize an internal clock to a server that is synchronized by a 1 pulse-per-second

Awards

SIM Time Scale

To support time and frequency metrology throughout the Americas, the Sistema Interamericano de Metrologia (SIM) Time and Frequency Metrology Working Group (TFMWG) maintains the SIM time scale (SIMT), the first continuously maintained multi-national ensemble time scale that is generated and published in real time (updated every hour). SIMT complements the world's official time scale, Coordinated Universal Time (UTC), by providing real time support to operational timing and calibration systems in the SIM region. The stability of SIMT is superior to most SIM local time scales and SIMT also provides a good approximation of UTC timing accuracy (±15 ns).

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Standard Reference Instruments (SRI)

NIST is consolidating its provision of reference instrumentation and devices into a new Standard Reference Instrumentation (SRI) program.

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Contacts

Group Leader