CGPM Votes to End Leap Seconds Starting May 20, 2027
The CGPM adopted a resolution ending leap second adjustments, expanding the allowed gap between Earth-rotation time and UTC to up to 3600 seconds.
The General Conference on Weights and Measures (CGPM) adopted a resolution to stop leap second adjustments at its 28th meeting in Versailles, France, according to zdnet.co.kr. The new time system will apply from May 20, 2027.
Under the change, the allowable difference between Earth-rotation-based time and UTC expands from about 1 second to a maximum of 3600 seconds, or 1 hour.
The decision was moved up from the previously agreed 2035 timeline, citing the increased possibility of a negative leap second and the growing importance of time synchronization for digital infrastructure.
Why the timeline changed
The leap second system was introduced in 1972, and time has been added by 1 second a total of 27 times since then, with the last adjustment made on December 31, 2016. No leap second has ever been deleted. In 2022, the 27th CGPM agreed to change the leap second adjustment method by 2035, and the BIPM estimated the probability that a negative leap second would be needed by 2035 at about 30 percent.
When a leap second was applied in 2012, internet services including Reddit and LinkedIn experienced outages, and Qantas airline flight operations were disrupted. Experts' evaluation of the decision was reported by Nature.
Quick answers
When does the new time system take effect?
The new time system will be applied from May 20, 2027, following the CGPM resolution adopted at its 28th meeting in Versailles, France.
How large can the gap between Earth-rotation time and UTC become?
The allowable difference will expand from about 1 second to a maximum of 3600 seconds, or 1 hour.
Why was the change moved up from 2035?
It was moved up due to the increased possibility of a negative leap second and the growing importance of time synchronization for digital infrastructure.