On October 15, 2026, the world’s measurement authorities adopted a resolution making Coordinated Universal Time continuous from May 20, 2027, and permitting it to drift as much as an hour from Earth’s rotation.
The flaw in synchronizing with Earth
The change resolves a tension built into modern timekeeping. International Atomic Time advances steadily from atomic clocks, while Earth's rotation varies. UTC, the global reference for civil time, was historically adjusted via leap seconds to stay within 0.9 seconds of the planet's rotation, UT1. Since 1972, timekeepers have inserted 27 leap seconds, the most recent at the end of 2016.
That occasional adjustment became a hazard as digital networks and critical infrastructure came to depend on predictably advancing timestamps. Software handles leap seconds inconsistently, threatening synchronization across satellite navigation, telecommunications, energy distribution, and finance. The prospect of a negative leap second—skipping a second, which has never been tested in practice—added urgency to eliminating the adjustments.
A faster path to continuity
In 2022, the General Conference on Weights and Measures agreed to increase the permitted gap between UTC and UT1 by 2035. Following extensive consultations with astronomers, metrology institutes, and network operators, the 2026 resolution brought continuous UTC forward to May 20, 2027, setting the maximum allowed drift at one hour.
Continuous UTC will tick steadily without irregular jumps, while specialists who require Earth's precise orientation can still obtain the difference via navigation messages and time services. The U.S. Naval Observatory confirmed that no leap second will be added in December 2026, making the 2016 adjustment the final one.
Parting ways with solar time
The long-term consequence is that clock time and the Sun's position will gradually diverge. The one-hour limit is designed to allow UTC to run uninterrupted for centuries without triggering a scheduled leap hour. The decision prioritizes predictable global time for modern infrastructure, leaving future generations to decide how to address any eventual divergence from solar time.