The world has decided to end the practice of adding leap seconds to the global timekeeping system, citing potential risks to computer systems and the possibility of a first-ever negative leap second.
The decision was approved by the General Conference on Weights and Measures (CGPM) at its 28th meeting in Versailles, France, on October 15, 2026. Under the new arrangement, Coordinated Universal Time (UTC) will become continuous from May 20, 2027, without the insertion of additional leap seconds.
Until now, leap seconds have occasionally been added to keep atomic time aligned with the Earth’s rotation. However, experts have warned that such adjustments can disrupt computer networks, digital infrastructure and other systems that depend on precise time synchronisation.
The decision also addresses concerns about a potential negative leap second, which would require removing a second from the global time scale. Such an adjustment has never been implemented and could pose significant technical challenges for systems that are not designed to accommodate it.
Coordinated Universal Time (UTC), the international standard used for civil timekeeping, is based on highly accurate atomic clocks. Astronomical time, by contrast, is determined by the Earth’s rotation, which does not maintain a perfectly constant speed.
Leap seconds were introduced to keep the two time scales closely aligned. However, the international metrology community has now agreed to allow the difference between them to grow rather than interrupt UTC with additional seconds.
Under the new arrangement, the difference between UTC and Earth’s rotational time will be allowed to reach up to one hour before a further adjustment becomes necessary.
The change is intended to make global timekeeping more stable and reliable for modern digital systems, telecommunications, satellite navigation and other technologies that rely on accurate time synchronisation.
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