Overview
- National delegates at the 28th General Conference on Weights and Measures in Versailles approved stopping leap seconds, a change set to take effect on 20 May 2027 that will keep Coordinated Universal Time (UTC) running without added or removed seconds.
- The resolution fixes UTC as a continuous atomic timescale and permits up to a one-hour difference with rotation-based time, so civil clocks will gradually diverge from solar time over many centuries.
- The move responds to operational risks: intermittent leap seconds have caused or threatened failures in computer systems, internet services, satellite navigation, aviation systems and banking networks when devices were unprepared for a one-second insertion or removal.
- A technical report cited by the proposal estimated about a 30% chance of needing a negative leap second within ten years, a risk that pushed metrologists to accelerate the end of leap seconds from the prior timeline.
- Practical arrangements will follow: around 500 national atomic clocks feed International Atomic Time (TAI) that underpins UTC, astronomy will continue to use rotation-based time for observations, and operators of critical infrastructure must update systems to work with an uninterrupted atomic timescale.