UTC (Coordinated Universal Time)
utc
The primary time standard by which the world regulates clocks and time, serving as the basis for civil timekeeping globally.
Leap Second
leap-second
Overview
A leap second is a one-second adjustment occasionally applied to UTC to account for the gradual slowing of Earth's rotation. Since their introduction in 1972, 27 leap seconds have been added. They are inserted at the end of June 30 or December 31, creating a minute that lasts 61 seconds (23:59:60 UTC).
Why They Exist
Atomic clocks measure time with extraordinary precision, but the Earth's rotation is gradually slowing due to tidal friction. Without leap seconds, UTC would slowly drift away from solar time. The International Earth Rotation and Reference Systems Service (IERS) monitors this difference and announces leap seconds approximately six months in advance.
Future Abolition
In November 2022, the General Conference on Weights and Measures voted to abolish leap seconds by 2035. The accumulated difference between atomic time and solar time will be allowed to grow until a larger correction (perhaps a "leap minute") is needed, likely not for over a century. Major tech companies like Google and Amazon already use "leap smearing" to gradually distribute the extra second over a longer period.
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