Leap Seconds Abolished; UTC to Drift Up to an Hour Before Correction

On 15 October, representatives from 69 countries voted at the International Bureau of Weights and Measures in Versailles to eliminate leap seconds from Coordinated Universal Time (UTC). The new rule allows UTC to diverge from astronomical time by up to one hour before a correction is applied, a change that will take effect on 20 May 2027. The decision follows growing concerns that inserting leap seconds can disrupt critical systems such as stock markets, telecommunications, GPS, and power grids, as past adjustments have caused website crashes and airline booking glitches. Scientists also noted that the Earth’s rotation has recently begun to accelerate, raising the possibility of a first‑ever negative leap second—a scenario that would be difficult to manage. In addition to the leap‑hour proposal, the BIPM meeting called for proposals to redefine the second using optical clocks and to develop a universal time standard for the Moon, signalling a broader shift in how time will be measured on Earth and beyond.