The world is preparing for a major change in timekeeping. From May 20, 2027, the international time system will stop using leap seconds under a decision adopted by the General Conference on Weights and Measures (CGPM).
The change aims to protect digital networks and critical infrastructure from timing errors. It will not add an hour to the day or change the time displayed on everyday clocks.
Why leap seconds are ending
Since 1972, scientists have added occasional leap seconds to Coordinated Universal Time (UTC) to keep it aligned with the Earth’s rotation. The planet does not rotate at a perfectly constant speed, while atomic clocks provide an extremely stable measure of time.
The last leap second was added on December 31, 2016. Since then, concerns have grown about the risks these adjustments pose to computer networks, telecommunications, electricity grids and satellite navigation.
Different technology providers handle leap seconds in different ways. These differences can cause timing inconsistencies across systems. Experts have also estimated a 30% probability that scientists may need to remove a second by 2035. Such a negative leap second has never been used and could disrupt systems that are not prepared for it.
The CGPM adopted the change on October 15, 2026, to make UTC continuous and more reliable for modern technology.
What changes in May 2027?
From May 20, 2027, the permitted difference between UTC and time based on the Earth’s rotation will increase to 3,600 seconds, or one hour. This will remove the need to insert leap seconds and help maintain a stable international time reference for centuries.
People will not need to reset their clocks or change their daily routines. The change affects the international time standard, not the familiar time displayed on phones and watches.
Scientists will continue to monitor the Earth’s rotation and measure its difference from UTC. That relationship remains important for applications such as astronomy and celestial navigation.
The International Bureau of Weights and Measures (BIPM) will work with international organizations to implement the decision and inform users.
For most people, the transition will go unnoticed. Its greatest impact will be behind the scenes, helping the digital systems that support modern life maintain a consistent and reliable time reference.
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