Timekeepers Vote to End the Leap Second
The International Bureau of Weights and Measures voted on Thursday to discontinue the leap second, ending a decades-long system that kept machine time aligned with the planet.
The leap second is an extra second added at irregular times so standard time tracks Earth's uneven rotation The Verge. It was built to reconcile two measures, astronomical time tied to rotation and atomic time tied to steady oscillators, by inserting a second when the two drifted apart.
The vote makes final a direction set in 2022, when BIPM members agreed to stop leap seconds on or before 2035. Discontinuation will take effect on May 20 next year, on World Metrology Day.
Earth's shifting rotation may soon require timekeepers to subtract a second rather than add one to keep the two scales aligned. Such a subtraction has never been attempted.
Infrastructure operators describe that untested step as a central concern. Past additions caused outages for Foursquare, Reddit, LinkedIn and Yelp. Meta, Google, Microsoft and Amazon have supported scrapping the system. The change aims to prevent infrastructure failures like the Y2K bug scare.
After the vote, timekeepers will use "leap hours," letting atomic and astronomical time drift until a full hour needs adding. That hour is not expected for about 3,000 years.
The decision comes from the body that keeps the base references. BIPM stands for the Bureau International des Poids et Mesures BIPM. It was established by the Metre Convention in 1875 and is home to the International System of Units (SI) and the global reference time scale UTC.
The broader context here is a trade between astronomical accuracy and predictable operation. Leap seconds kept the two times close, but they broke the assumption in computer systems that time moves forward uniformly. For distributed infrastructure, that unevenness is expensive.
Looking at what this means in practice, the move to leap hours puts the correction so far ahead that it stops being an engineering factor. Systems can treat UTC as effectively continuous for procurement, protocol design and operating life. The drift is real, but it builds over millennia, not maintenance windows.
