UTC is itself derived from International Atomic Time (TAI) from which it differs only by a whole number of seconds, currently 32. UTC is the legal basis of time in the world. By international convention, UTC is equivalent to GMT, however their measurements differ: GMT is measured from midday, whereas UTC is measured from midnight. On 1st January 1982, following a decision by the International Telecommunication Union (UIT), GMT was replaced by UTC (Coordinated Universal Time), in order to correct universal time, in which the duration of the day is not constant throughout the year due to the Earth’s rotation on its axis. China for example has adopted a single time for its entire territory, while India encompasses a time difference of five and a half hours. However, time-zones follow national frontiers and some countries depart from universal time. The GMT system was adopted internationally on 1st January 1885. GMT is the mean solar time calculated at midday. Since one day lasts 24 hours, the terrestrial globe is “divided” into 24 zones whose longitude differs by 15° (one hour), with the middle of each zone dictating the time in the latter. This meridian was also used to determine time-zones, and original time or GMT (Greenwich Mean Time). Greenwich, located in the south-east suburbs of London, was until 1946 home to the Royal Observatory of the same name. All rights reserved.After some tough discussions, particularly between the French and the British, the Washington international conference in October 1884 adopted the Greenwich meridian as the prime meridian for measuring longitude. Click here for information on 24 hour clocks If you're like many radio hobbyists, you will soon add a second clock set to UTC to your collection of radio gear. If you live in the central or eastern United States, and those frequencies aren't usable, you can tune to station CHU, in Ottawa, Ontario, Canada on 3330, 7335 780 kHz, to hear the current UTC time. WWV uses a man's voice to give the time, while WWVH uses a female voice. To hear the latest time in UTC, you can tune to stations WWV, in Fort Collins, Colorado and WWVH, Kauai, Hawaii on 2500, 5000, 1000 kHz to hear the time announced in UTC each minute. Since the date is also UTC, you need to listen at 10:00 p.m. on Saturday, however, you won't hear the program. You do the math, and find that 0400 UTC is equal to 10:00 p.m. Suppose your local time zone is Central standard,Īnd you want to hear a shortwave program scheduled to be broadcast at 0400 UTC Saturday. timezones.Ī major source of confusion when using UTC is that the date also follows UTC. The second table is direct conversion from UTC to U.S.A. The number of hours to subtract from local time zones in North America in order to convert West of the zero meridian to the international date line (which includes all of NorthĪmerica), hours are subtracted from UTC to convert to local time. To convert UTC to local time, you have to add or subtract hours from it. Minute later is 0000 ("zero hundred"), and the start of a new UTC day. The time one minute afterġ259 is 1300 (pronounced "thirteen hundred"). "1:00 a.m." in UTC is expressedĪs 0100, pronounced "zero one hundred." Fifteen minutes after 0100 is expressedĪs 0115 thirty-eight minutes after 0100 is 0138 (usually pronounced "zero one UTC uses a 24-hour system of time notation. Improvements in accuracy, however, the same principles used in GMT have been carried over Reliable, accurate standard for scientific and navigational purposes. Precise atomic clocks, shortwave time signals, and satellites to ensure that UTC remains a GMT became a world time and date standard because it was usedīy Britain's Royal Navy and merchant fleet during the nineteenth century. Greenwich mean time was based upon the time at the zero degree meridian that crossed All of the times and dates found here at Operators, shortwave listeners, the military, and utility radio services are also big International shortwave broadcasters in their broadcast and program schedules. Times), "universal time," and "world time." Refer to it include "Zulu time" (after the "Z" often used after UTC This was formerly known as Greenwich mean time (GMT). This standard is coordinated universal time, abbreviated UTC. Since radio signals can cross multiple time zones and the internationalĭate line, some worldwide standard for time and date is needed.
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