Versailles backs replacing leap seconds with a leap hour — The Guardian
Delegates from 69 countries at a conference of the International Bureau of Weights and Measures in Versailles, France, voted to replace leap seconds with a leap hour. The decision, which is due to take effect next year, is intended to reduce risks for computer and other technical systems that may incorrectly process minutes lasting 59 or 61 seconds.
As The Guardian reports, the new approach will allow Coordinated Universal Time (UTC) to diverge from astronomical time by up to one hour. According to experts, the need for a leap hour will not arise for at least thousands of years.
Why leap seconds are being abandoned
Leap seconds have been used since 1972 to synchronize UTC with the Earth’s rotation. Since then, 27 such seconds have been added. Atomic clocks operate with exceptional stability, while the planet’s rotational speed changes under the influence of processes in its molten core, ocean movements, jet streams and other natural factors.
Overall, the Earth is rotating more slowly: at the time of the asteroid that caused the extinction of the dinosaurs, a day lasted about 23.5 hours. However, over the past decade, the planet’s rotation has accelerated. This meant that the first negative leap second — the removal of one second from UTC — could have been needed in the next ten years. The probability of such a scenario was estimated at 30%.
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Risks to digital infrastructure
Setnam Shemar, chief scientist of the Time and Frequency Department at the UK’s National Physical Laboratory, said that a leap hour would reduce risks for systems and infrastructure that depend on precise time, while preserving the connection between the global time system and the Earth’s rotation.
According to him, after a leap second was added in 2012, some operating systems were unable to cope with 61 seconds in a minute: servers froze and systems failed. At the time, Reddit and LinkedIn, among others, experienced disruptions, while Qantas flights were delayed. Negative leap seconds pose an even greater risk, Shemar said, as software may not have been tested for such a scenario.
Christian Bizouard, head of the IERS Earth Orientation Centre in Paris, welcomed the decision but noted that it effectively postpones the problem for people in the distant future.
