This public service is cooperatively provided by the two time agencies of the United States: a Department of Commerce agency, the National Institute of Standards and Technology (NIST), and the U. S. Naval Observatory (USNO). Readings from the clocks of these agencies contribute to world time, called Coordinated Universal Time (UTC). The time maintained by both agencies should never differ by more than 0.0000001 seconds from UTC.

The Time and Frequency Division, part of NIST's Physics Laboratory, maintains the standard for frequency and time interval for the United States, provides official time to the United States, and carries out a broad program of research and service activities in time and frequency metrology.

The United States Naval Observatory is an Echelon-IV operational command reporting to the Commander, Navy Oceanography and Meteorology Command. The U.S. Naval Observatory (USNO) provides a wide range of astronomical data and products, and serves as the official source of time for the U.S. Department of Defense, and a standard of time for the entire U.S. Founded in 1830 as the U.S. Navy Depot of Charts and Instruments, USNO is recognized as the world's foremost authority on spatial and temporal reference frames. USNO is headquartered in Washington, D.C., and operates a dark-sky observing station near Flagstaff, Arizona (NOFS). It also has a small detachment activity, the Alternate Master Clock facility (AMC), located at Schriever Space Force Base in Colorado Springs, Colorado. Washington, D.C.