Skip to main content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.


The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Time Measurement



Michael A. Lombardi


An overview of time metrology, with emphasis on time interval measurements, and time synchronization. It covers the evolution of clocks and timekeeping, time scales, the fundamentals of time measurement, and the various time transfer technique used to synchronize and compare clocks at remote locations. The original version of this chapter was written in 1997 (published in 1999), and about 70% of the material has been revised for the forthcoming 2nd edition of the "Measurement, Instrumentation, and Sensors Handbook".
The Measurement, Instrumentation, and Sensors Handbook (2nd edition)
Ch. 41
Publisher Info
CRC Press, Boca Raton, FL


atomic clocks, GPS, time, time scale, time transfer
Created February 3, 2014, Updated February 19, 2017