[REVISION HISTORY]

CGPM votes to abolish leap seconds

Updated 20 times since CLSTR started tracking revisions of this situation.

What changed

2026-10-20 14:23 UTC → 2026-10-26 18:23 UTC · added ~~removed~~

The General Conference on Weights and Measures (CGPM) has officially approved Resolution 5 to abolish the leap second, a move designed to protect digital infrastructure from synchronization errors. During its 28th meeting in Versailles, France, the CGPM confirmed that the practice of using periodic one-second adjustments to reconcile Coordinated Universal Time (UTC) with the Earth’s irregular rotation (UT1) will end. This decision addresses long-standing concerns regarding technical disruptions in telecommunications, financial markets, energy distribution, and space projects. Since 1972, 27 leap seconds have been ~~used~~ added to ~~synchronize~~ keep atomic ~~clocks~~ time in sync with astronomical time. However, recent ~~fluctuations in Earth’s~~ observations show that the Earth's rotation speed has become increasingly variable, with some days being shorter than the standard 24 hours. This variability raised the risk of a “negative leap second,” which digital systems are currently unequipped to handle. Under the new regulation, the maximum allowable discrepancy between atomic time and astronomical time will increase from less than one second to up to 3,600 seconds (one hour). This shift allows for a more stable, continuous time scale, potentially replacing frequent small adjustments with an “intercalary hour” or “leap hour” that may not be required for ~~centuries or even millennia.~~ centuries. The transition to this new framework is scheduled to take effect on May 20, 2027. In support of this transition, the International Bureau of Weights and Measures (BIPM) has voted to uphold the abolition. Noël Dimarcq, president of the BIPM’s time and frequency committee, noted that the new protocol will wait until a full hour is required to re-synchronize with the planet’s rotation, a change that may not be necessary for centuries. In October 2026, international delegates from 69 countries reaffirmed this direction during a BIPM conference in France, voting to phase out leap seconds in favor of the “leap hour” approach to reduce software errors in systems relying on precise timekeeping.

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