Koordinoitu yleisaika

Koordinoitu yleisaika (UTC) on ensisijainen aikajärjestelmä, jolla maailman aika määrätään. Se pysyy noin sekunnin sisällä keskimääräisestä aurinkoajasta nollapituuspiirillä, eikä sitä ole sidottu kesäaikaan. Joissakin maissa termiä GMT (Greenwich Mean Time) käytetään usein UTC:n synonyyminä. 

Ensimmäinen koordinoitu yleisaika hyväksyttiin epävirallisesti 1. tammikuuta 1960, mutta UTC:n virallinen lyhenne ja nimi hyväksyttiin vasta vuonna 1967.

Lyhenteen alkuperä 
Jos UTC-lyhenne otettaisiin suoraan englanninkielisistä sanoista Coordinated Universal Time, siitä tulisi CUT, ja jos se otettaisiin ranskankielisestä vastineesta temps universel coordonné, siitä tulisi TUC. Kansainvälinen televiestintäliitto kuitenkin halusi, että lyhenne ei viittaisi kumpaankaan kieleen, joten kompromissiksi valittiin UTC (Universal Time, Coordinated eli universel, temps coordonné).

Aikavyöhykkeet

Kirjallisuutta 

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