World abandons leap seconds in favour of leap hours
At the General Conference on Weights and Measures in Versailles, delegates from 69 countries voted to eliminate the leap second, which has been used since the 1970s to keep official time synchronized with Earth's rotation. From 20 May 2027, Coordinated Universal Time will operate continuously, with a leap hour to be introduced only when necessary, potentially not for thousands of years.
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Following three decades of discussion, the world's timekeeping authorities have voted to end the leap second, an adjustment that has been periodically inserted into official time since the 1970s to maintain synchronization with Earth's irregular rotation. The vote took place on Thursday at the General Conference on Weights and Measures, held by the International Bureau of Weights and Measures in Versailles, France, with delegates from 69 countries participating.
The leap second has created recurring problems for technical systems. When inserted, it forces computer systems, satellites and navigation networks to process minutes containing either 59 or 61 seconds instead of the standard 60. This irregularity has been responsible for numerous software errors and service outages across various industries and infrastructure systems.
Beginning 20 May 2027, Coordinated Universal Time will run without interruption. The new system replaces the leap second with a much less frequent adjustment called a leap hour. This change allows UTC to diverge from Earth's rotation-based timescale by up to 3,600 seconds before any correction becomes necessary.
Experts argue that this adjustment removes a significant source of technical risk while preserving the practical value of UTC as the global reference standard for computers, telecommunications, aviation, shipping and satellite navigation systems. Since Earth's rotation slows only gradually, scientists estimate that the first leap hour may not be required for thousands of years, making this change largely inconsequential for current and foreseeable future generations.
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