In telecommunication, DOD master clock is the master clock to which time and frequency measurements for the United States Department of Defense are referenced, i.e. , are traceable.

Note 1: The U.S. Naval Observatory master clock is designated as the DOD Master Clock.

Note 2: The U.S. Naval Observatory master clock is one of the two standard 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 (NIST) master clock.

Source: from Federal Standard 1037C and from MIL-STD-188