Greenwich Mean Time


Greenwich Mean Time
GMT.

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      the name for mean solar time of the longitude (0°) of the Royal Greenwich Observatory in England. The meridian at this longitude is called the prime meridian or Greenwich meridian.

      Greenwich Mean Time was used for clearly designating epoch by avoiding confusing references to local time systems (zones). In accord with astronomical tradition, astronomers had always used Greenwich Mean Astronomical Time (GMAT)—the same as GMT but with the day beginning at noon. In 1925 GMT was adopted by astronomers so that the astronomical day began at midnight, the same time as the civil day. Some confusion in terminology resulted, though, and in 1928 the International Astronomical Union changed the designation of the standard time of the Greenwich meridian to Universal Time, which remains in general use in a modified form as Coordinated Universal Time (UTC). The term GMT is still used for some purposes—e.g., navigation in English-speaking countries.

Jonathan D. Betts
 

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Universalium. 2010.

Look at other dictionaries:

  • Greenwich Mean Time — (GMT) is a term originally referring to mean solar time at the Royal Observatory in Greenwich, London. It is now often used to refer to Coordinated Universal Time (UTC) when this is viewed as a time zone, although strictly UTC is an atomic time… …   Wikipedia

  • Greenwich (mean) time — or Greenwich time n. mean solar time of the meridian (0° longitude) at Greenwich, England: see also COORDINATED UNIVERSAL TIME, UNIVERSAL TIME * * * …   Universalium

  • Greenwich (mean) time — or Greenwich time n. mean solar time of the meridian (0° longitude) at Greenwich, England: see also COORDINATED UNIVERSAL TIME, UNIVERSAL TIME …   English World dictionary

  • Greenwich (mean) time — or Greenwich time n. mean solar time of the meridian (0° longitude) at Greenwich, England: see also COORDINATED UNIVERSAL TIME, UNIVERSAL TIME …   English World dictionary

  • Greenwich Mean Time — ► NOUN ▪ the mean solar time at the Greenwich meridian, used as the standard time in a zone that includes the British Isles. ORIGIN from Greenwich in London, former site of the Royal Observatory …   English terms dictionary

  • Greenwich Mean Time — Green‧wich Mean Time [ˌgrenɪtʆ ˈmiːn taɪm, ˌgrɪ , nɪdʒ ] ➔ GMT * * * Greenwich Mean Time UK US noun [U] MEASURES ► GMT(Cf. ↑GMT) …   Financial and business terms

  • Greenwich Mean Time — (kurz GMT) [ˌgrenɪtʃ ˈmiːn taim; ɪdʒ], zu Deutsch: mittlere Greenwich Zeit, ist die mittlere Sonnenzeit am Nullmeridian. Die Greenwich Mean Time war von 1884 bis 1928 Weltzeit, in dieser Funktion ist sie heute von der Koordinierten Weltzeit UTC… …   Deutsch Wikipedia

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  • Greenwich mean time — Temps moyen de Greenwich « GMT » redirige ici. Pour les autres significations, voir GMT (homonymie) …   Wikipédia en Français

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