Leap second: Difference between revisions

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Revision as of 14:14, 8 February 2005

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A '''leap second''' is a one-[[second]] adjustment to [[civil time]] in order to keep it close to the [[mean solar time]].

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|align=center| '''List of leap seconds'''

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# [[31 December]] [[1998]]

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Civil clock time is based on [[UTC|"Coordinated Universal Time" (UTC)]], which is maintained by extremely precise [[atomic clock]]s. In contrast, the rotation of the Earth, measured by the [[UT1]] timescale, is irregular; the solar day is gradually but unevenly becoming longer, mainly due to the [[tidal acceleration]] of the [[Moon]]. In order to keep solar time close to civil time, UTC is corrected by a leap of 1 second. The rotation of the earth is now already a bit slower than it should be in order to have a day of exactly 24 hours. If the rotation would now remain constant, leap seconds would be necessary in regular intervals. Because the earth is continually slowing down, the interval between two leap seconds is becoming smaller over longer timescales. 50000 years in the future one can expect to have more than one leap second every day if the time system is not going to be changed.