leap second

noun

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.

leap second

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

leap second

A second of time, as measured by an atomic clock, added to or omitted from official timekeeping systems annually to compensate for changes in the rotation of the Earth.
See more at coordinated universal time

leap second

A second inserted into the year to make up for the fact that the Earth's rotation is slowing down.

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Scientists know when to insert a leap second by comparing the Earth's rotation to an atomic clock.

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First recorded in 1970–75

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Examples have not been reviewed.

This is known as a "negative leap second."

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There’s even a leap second occasionally, but there’s no hullabaloo when that happens.

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Devised in 1972 and used 27 times since, the leap second wreaks havoc with modern-day telecommunications, banking, and other networks.

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Since 1972, whenever the two time systems have drifted apart by more than 0.9 seconds, a leap second has been added.

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The time has come — or will come, in 2035 — to abandon the leap second.

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