leap second


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leap second

n.
A second of time, as measured by an atomic clock, added to or omitted from official timekeeping systems periodically to compensate for small changes in the rotation of the earth and therefore the length of a solar day.

leap second

n
(Units) a second added to or removed from a scale for reckoning time on one particular occasion, to synchronize it with another scale

leap′ sec`ond


n.
an extra second intercalated into the world's timekeeping system about once a year, made necessary by the gradual slowing down of the earth's rotation.
[1970–75]
ThesaurusAntonymsRelated WordsSynonymsLegend:
Noun1.leap second - a second (as measured by an atomic clock) added to or subtracted from Greenwich Mean Time in order to compensate for slowing in the Earth's rotation
s, sec, second - 1/60 of a minute; the basic unit of time adopted under the Systeme International d'Unites
References in periodicals archive ?
The last time a leap second was added to clocks was June 30, 2015.
Leap seconds have been added to our days since the 1970s and will continue to be added for years to come.
A leap second was added most recently on 30 June 2015 at 23:59:60 UTC.
Or I would make the day the leap second falls on an I-pad free day for my kids so that's one extra second they don't get to waste
However, the rotation speed of the Earth fluctuates unpredictably, and has been found to even slow down due to friction caused by the ocean tides -- hence the need for a leap second.
59 Greenwich Mean Time (GMT) on June 30, the earth will experience a minute that will last 61 seconds -- the extra second is called the leap second.
Although leap seconds caused by the need to compensate for the earth's rotation are extremely rare occurrences -- the last whole second adjustment would have happened in 1820 had atomic clocks and NTP servers existed -- there have in fact been 25 leap seconds for other reasons since the beginning of atomically-measured time in 1971.
The so-called leap second was added to electronic clocks at midnight universal time on Saturday, with atomic clocks reading 23 hours, 59 minutes and 60 seconds before then moving on to Greenwich Mean Time.
To stop things getting out of hand, the International Telecommunications Union (ITU) adds a leap second to atomic time every few years.
Leap second to be inserted to adjust for earth's rotation
For accuracy, it adds a leap second to the year when necessary, making the last minute of June or December 61 seconds long instead of the usual 60.
But our world's clocks are still set by the Sun and stars, and that will continue unless the leap second is abolished (S&T: January 2006, page 134).