Global Clocks Drop Leap Seconds for Good
The General Conference on Weights and Measures has adopted a change ending leap seconds in Coordinated Universal Time.
Updated on Nov. 4, 2026 in Space
Live Poll
Do you expect changes to international timekeeping to affect your daily life?
The General Conference on Weights and Measures adopted a decision on October 15, 2026, ending the addition of leap seconds to Coordinated Universal Time. The permitted difference between UTC and Earth's rotation-based time will increase to one hour on May 20, 2027.
Why it matters
Leap seconds have been added to UTC since 1972, but concerns about timing errors in computer networks, telecommunications, electricity grids and satellite navigation have grown. The change is intended to protect digital networks and critical infrastructure while keeping a stable international time reference.
The decision sets the permitted gap between UTC and Earth's rotation at 3,600 seconds, a limit that removes the need to insert leap seconds. Experts estimate a 30% probability that a negative leap second may be needed by 2035.
The players
General Conference on Weights and Measures
The international body that adopted the decision ending leap seconds in Coordinated Universal Time.
Bureau International des Poids et Mesures
The Sèvres, France-based organization that will implement the decision with international partners.
The details
The change does not add an hour to the day or alter everyday clock times. Different technology providers handle leap seconds in different ways, and the Bureau International des Poids et Mesures will work with international organizations to implement the decision.
Timeline
1972: Leap seconds first added to UTC.
December 31, 2016: Last leap second added.
October 15, 2026: General Conference on Weights and Measures adopts the change.
May 20, 2027: UTC difference limit becomes one hour and leap seconds stop.
2035: Estimated 30% chance a negative leap second may be needed.
Roadmap
The decision reverses the 1972 policy that introduced leap seconds into Coordinated Universal Time, which was adopted to reconcile atomic time with Earth's uneven rotation. Ending leap seconds replaces that correction with a larger permitted gap that is intended to keep international time stable for centuries.
The change does not add an hour to the day or alter everyday clock times, so most people will see no difference on their devices. Its practical effect is on telecommunications, electricity grids and satellite navigation systems that depend on precise timing.
The takeaway
Most people will notice nothing when leap seconds end, since everyday clocks keep their current times. The shift matters most to the networks and infrastructure that rely on exact timing.
What happens next
The permitted UTC difference limit becomes one hour on May 20, 2027, when leap seconds stop being added.
Further reading
For more on how timekeeping connects to orbital and navigation systems, see Space.
Source note: This article includes information reported by GreekReporter.
Live Poll
Do you expect changes to international timekeeping to affect your daily life?
