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cycle clockNIST Web Clock Frequently asked questions (FAQ)

What time is it?

How to get the time using a telephone, computer or radio signals.

NIST Radio Broadcasts

Descriptions and uses of radio signals from WWV, WWVB and WWVH.

NIST time

How is UTC(NIST) related to Coordinated Universal Time (UTC)

International Atomic Time (TAI), Greenwich Mean Time (GMT)

USNO time, GPS time and Zulu time?

Local Time

Daylight saving time rules, exceptions and legislation.

Time zones, borders, abbreviations and relationship to U.S. postal zip codes.  

Leap seconds

What leap seconds are, how they are implemented and their future.

Timekeeping and Clocks  

How clocks work.

Cesium clocks, why we need precise time and frequency.

Stopwatch calibrations, calendars and history.

Times of day

How to use a.m./p.m. vs. noon/midnight.

Sunrise/sunset times and definitions of dusk/dawn/twilight.

If you have a question that is not addressed here, let us know.