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USNO Master Clock

The USNO Master Clock is the underlying product for all of our precise time and time interval products. The timing reference produced by this timing ensemble is called UTC(USNO). This timing reference is mandated to be the precise time reference for all of the DoD.

USNO Master Clock Description

Technical information about the physical components that make up our timing ensemble.

USNO Time Scales

Descriptions of the time scales determined at USNO and their relationships.

International Time Scales and the BIPM

Information about the relationship between international time scales and the USNO products.  This section includes data files and plots of these time scales.

Definitions of Systems of Time

Definitions of systems for determining and referencing times.  These range from atomic time scales to the rotation of the Earth.


Commander, Naval Meteorology and Oceanography Command | 1100 Balch Blvd. | Stennis Space Center, Mississippi 39529

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