The Department of Defense master clock is the atomic master clock to which

time Time is the continued sequence of existence and events that occurs in an apparently irreversible succession from the past, through the present, into the future. It is a component quantity of various measurements used to sequence events, ...

and

frequency Frequency is the number of occurrences of a repeating event per unit of time. It is also occasionally referred to as ''temporal frequency'' for clarity, and is distinct from ''angular frequency''. Frequency is measured in hertz (Hz) which is eq ...

measurements for the

United States Department of Defense The United States Department of Defense (DoD, USDOD or DOD) is an executive branch department of the federal government charged with coordinating and supervising all agencies and functions of the government directly related to national sec ...

are referenced. Located in Washington D.C., the

U.S. Naval Observatory United States Naval Observatory (USNO) is a scientific and military facility that produces geopositioning, navigation and timekeeping data for the United States Navy and the United States Department of Defense. Established in 1830 as the Depo ...

master clock is designated as the "DOD Master Clock". It is one of the two

standard Standard may refer to: Symbols * Colours, standards and guidons, kinds of military signs * Standard (emblem), a type of a large symbol or emblem used for identification Norms, conventions or requirements * Standard (metrology), an object th ...

time and frequency references for the U.S. Government in accordance with Federal Standard 1002-A. The other standard time and frequency reference for the U.S. Government is the

National Institute of Standards and Technology The National Institute of Standards and Technology (NIST) is an agency of the United States Department of Commerce whose mission is to promote American innovation and industrial competitiveness. NIST's activities are organized into physical s ...

(NIST) master clock. In 2018, it was proposed to replace the existing Clock House building it's housed in, designed by Richard Morris Hunt, with a new facility. The U.S. Naval Observatory also maintains an alternate clock designated "USNO Alternate Master Clock" at

Schriever Air Force Base Schriever Space Force Base, previously Schriever Air Force Base, Falcon Air Force Base, and Falcon Air Force Station, is a base of the United States Space Force located approximately east of Peterson Space Force Base near Colorado Springs in ...

Colorado Colorado (, other variants) is a state in the Mountain states, Mountain West subregion of the Western United States. It encompasses most of the Southern Rocky Mountains, as well as the northeastern portion of the Colorado Plateau and the wes ...

References

{{reflist Clocks in the United States United States Department of Defense