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UTC deviates from TAI by a number of whole seconds. As of 1 January 2017, immediately after the most recent leap second was put into effect, [4] UTC has been exactly 37 seconds behind TAI. The 37 seconds result from the initial difference of 10 seconds at the start of 1972, plus 27 leap seconds in UTC since 1972.
While TT is only theoretical, it is commonly realized as TAI + 32.184 seconds where TAI is UTC plus the current leap seconds, so ΔT = UTC − UT1 + (leap seconds) + 32.184 s. This can be rewritten as ΔT = (leap seconds) + 32.184 s − DUT1, where DUT1 is UT1 − UTC.
The offset 32.184 seconds was the 1976 estimate of the difference between Ephemeris Time (ET) and TAI, "to provide continuity with the current values and practice in the use of Ephemeris Time". [9] TAI is never revised once published and TT(TAI) has small errors relative to TT(BIPM), [6] on the order of 10-50 microseconds. [10] The GPS time ...
The current version of UTC is defined by International Telecommunication Union Recommendation (ITU-R TF.460-6), Standard-frequency and time-signal emissions, [39] and is based on International Atomic Time (TAI) with leap seconds added at irregular intervals to compensate for the accumulated difference between TAI and time measured by Earth's ...
Coordinated Universal Time (UTC) is the result of comparing clocks in national laboratories around the world to International Atomic Time (TAI), then adding leap seconds as necessary. TAI is a weighted average of around 450 clocks in some 80 time institutions. [62] The relative stability of TAI is around one part in 10 16.
International Atomic Time (TAI), in which every day is precisely 86 400 seconds long, ignores solar time and gradually loses synchronization with the Earth's rotation at a rate of roughly one second per year. In Unix time, every day contains exactly 86 400 seconds. Each leap second uses the timestamp of a second that immediately precedes or ...
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Screenshot of the UTC clock from time.gov during the leap second on 31 December 2016.. A leap second is a one-second adjustment that is occasionally applied to Coordinated Universal Time (UTC), to accommodate the difference between precise time (International Atomic Time (TAI), as measured by atomic clocks) and imprecise observed solar time (), which varies due to irregularities and long-term ...