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About UTC and Time
This information was written and supplied by Howard Barnes, of the


There are 7 Universal Times (all within 1 second of each other), and UTC is the "coordinated version of 'Universal Time'", hence the word order of Coordinated Universal Time. It was named such in 1964. The abbreviation UTC is a language-independent international abbreviation, it is neither English nor French. It means both "Coordinated Universal Time" and "Temps Universel Coordonné".

Proper GMT was originally measured from Greenwich mean mid-day, not mid-night [proof: Astronomical Almanacs 1984 onwards, page B5]
UTC isn't the same as GMT, as UTC is an ATOMIC time-scale, while GMT (strictly speaking UT1 [UT-one]) is tied to the rotation of the Earth in respect to the fictitious 'mean Sun'. UTC is, however, kept within 0.9 seconds of UT1, by virtue of leap seconds.
For the term 'Coordinated Universal Time' (UTC), I refer you to the following websites:

(see the BIPM Time Section in the two links below)

The world's GOVERNING BODY for civil atomic time-scales here and here
The International Earth Rotation Service

The Royal Observatory Greenwich

A good history of UTC and GMT

US. National Institute of Standards & Technology

UK's National Physical Laboratory

The US Naval Observatory here, here, and here.

The International Telecommunication Union

You can also listen to NIST's short-wave Radio Station WWV on 2.5, 5, 10, 15 or 20MHz; or phone +1-303-499-7111 (a toll call to Boulder, Colorado) for accurate time of day and CORRECT word order. Time is also available from Canadian Radio Station CHU on 3.33, 7.335 or 14.67 MHz (in both English and French).

The GDSO three-panel two-fold PDF pamphlet "A Briefer History of Time" is available here. Should this link fail to operate, go here, then click on time.pdf (near the bottom right corner).

Here is some info from the "Basics of Space Flight tutorial.
The information on this page was obtained from NASA's JPL (Jet Propulsion Laboratory) web site. Any questions or complaints about this UTC explanation should be directed to them at this link.

JPL's page created on 11/21/01