![]() In 1960 the U.S. Naval Observatory, the Royal Greenwich Observatory, and the UK National Physical Laboratory coordinated their radio broadcasts so time steps and frequency changes were coordinated, and the resulting time scale was informally referred to as "Coordinated Universal Time". National Bureau of Standards and U.S. Naval Observatory started to develop atomic frequency time scales by 1959 these time scales were used in generating the WWV time signals, named for the shortwave radio station that broadcasts them. By National Physical Laboratory - Public Domain In 1955 the caesium atomic clock was invented. This provided a form of timekeeping that was both more stable and more convenient than astronomical observations. In 1928, the term Universal Time (UT) was introduced by the International Astronomical Union (IAU) to refer to GMT with the day starting at midnight. Until the 1950s, broadcast time signals were based on UT, and hence on the rotation of the Earth. It persisted much longer elsewhere because it was mentioned at the 1884 conference. In 1884 the Greenwich Meridian was used for two-thirds of all charts and maps as their Prime Meridian. In contrast, astronomical GMT began at mean noon, 12 hours after mean midnight of the same date until 1 January 1925, whereas nautical GMT began at mean noon, 12 hours before mean midnight of the same date, at least until 1805 in the British Navy. It started from 0 hours at mean midnight. This agreed with civil Greenwich Mean Time (GMT), used in Great Britain since 1847. Greenwich Mean Time (GMT) is still the standard time for the Prime Meridian (Zero Longitude) and civil time in UK when Daylight Saving Time is not in use.Īt the 1884 International Meridian Conference held in Washington, DC, USA, local mean solar time at the Royal Observatory, Greenwich in England was chosen to define the Universal Day. ![]() UTC - Universal Time Coordinated What is Coordinated Universal Time?Ĭoordinated Universal Time ( UTC ) replaced Greenwich Mean Time (GMT) as the World Standard for time in 1972. UTC is based on atomic measurements, while GMT is based on Earth's rotation. ![]()
0 Comments
Leave a Reply. |
Details
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |