Universal Time

Universal Time (UT) is a timescale based on the rotation of the Earth. It is a modern continuation of the Greenwich Mean Time (GMT), i.e., the mean solar time on the meridian of Greenwich, England, which is the conventional 0-meridian for geographic longitude. GMT is sometimes used, incorrectly, as a synonym for UTC. The old GMT has been split, in effect into UTC and UT1.

References

• Federal Standard 1037C and from the Department of Defense Dictionary of Military and Associated Terms and from time scale
• Galison, Peter. Einstein's clocks, Poincaré's maps: Empires of time. New York: W.W. Norton & Company, 2003. ISBN 0393020010. Discusses the history of time standardization.
• O'Malley, Michael. Keeping watch: A history of American time. Washington: Smithsonian, 1996. ISBN 1560986727
• Seidelman, P. Kenneth, ed. Explanatory supplement to the Astronomical Almanac. Mill Valley, California: University Science Books, 1992. ISBN 0935702687.