The world's timekeepers have voted to stop adding leap seconds to clocks, ending a 54-year practice of nudging official time to match Earth's spin. Member states of the General Conference on Weights and Measures approved the change on Oct. 15 at their 28th meeting near Paris, according to Nature.

The planet itself forced the timing. Earth's rotation has been running slightly faster than expected in recent years, raising the real possibility that timekeepers would need the first-ever negative leap second, a skipped second that no global computer network has been built to handle.

Under the new rule, Coordinated Universal Time, the atomic standard behind phones, financial markets and power grids, will be allowed to drift up to one hour from time based on Earth's rotation before any correction. The change takes effect on May 20, 2027, according to Scientific American.

A Planet That Keeps Changing Its Pace

Earth does not spin at a perfectly steady rate. Tidal friction from the moon slows it gradually over centuries, but shorter-term shifts in the planet's molten core, oceans, atmosphere and ice can speed it up or slow it down by milliseconds. Those tiny differences add up over months and years.

Since 1972, a leap second has been inserted whenever atomic time and Earth's rotation drifted close to a one-second gap. That has happened 27 times, most recently at the end of 2016, according to CBC News. All of them added a second because Earth was running slow.

Recent acceleration reversed that pressure. Instead of adding time, timekeepers began preparing for the possibility of removing a second, something never done before. Patrizia Tavella, director of the Time Department at the International Bureau of Weights and Measures, told Scientific American in an earlier interview that waiting until 2035 carried "30 percent risk of a negative leap second."

The physics behind the speed-up is still being studied. Research reported in Nature in 2024 found that melting polar ice, driven by climate change, has slowed Earth's rotation by shifting mass toward the equator, partly offsetting the acceleration from the core. A separate Nature study published in September linked multidecadal changes in day length to gravitational interactions inside the planet.

Retiring a Second After 30 Years of Debate

The vote accelerates a decision made in 2022, when the same conference agreed to end leap seconds by 2035. Fear of a negative leap second before that deadline prompted the faster timetable, as Nature reported in August.

The resolution passed by majority vote rather than unanimously. Georgette Macdonald, director general of the National Research Council of Canada's Metrology Research Centre, whose country supported it, told Nature the decision will "ensure the continuity and relevance of UTC for centuries to come."

A leap hour may never practically arrive. Scientists cited by Scientific American predict that the gap between atomic time and Earth's rotation will not reach an hour for more than 1,000 years, which effectively passes the question to future generations. Nature described the replacement as unlikely to be needed for thousands of years.

Some users of Earth-linked time will need to adapt. Astronomers who aim telescopes using rotation-based time already apply separate corrections, and Russia's GLONASS satellite navigation system, unlike GPS, has built leap seconds into its operations. The U.S.-run GPS keeps its own continuous time scale and does not insert leap seconds.

Fewer Glitches for Phones, Banks and Websites

For everyday users, the change should be invisible, and that is the point. Past leap seconds have caused real disruptions. A 2012 leap second contributed to crashes at sites including Reddit and LinkedIn and delayed Qantas flights, and a 2017 leap second triggered a software bug at internet company Cloudflare.

Large tech firms responded by smearing leap seconds across many hours, but different companies used different methods, leaving clocks slightly out of step during each event. A negative leap second would have been untested territory for most of that infrastructure, which is why timekeepers treated even a modest probability as unacceptable.

Ending leap seconds lowers that risk for systems that rely on precise, synchronized time. That includes stock and banking networks that timestamp trades, cellular networks, and electric grids that coordinate generation across large regions. No action is required from households, and phones and computers will continue to set their time automatically. Businesses that run their own time servers may want to confirm with vendors how their systems will handle the transition.

The Countdown to May 2027

Implementation now moves to the International Bureau of Weights and Measures, the International Earth Rotation and Reference Systems Service, and national time agencies such as the U.S. National Institute of Standards and Technology. They will prepare for continuous UTC beginning May 20, 2027, which is World Metrology Day.

The rotation service, which monitors Earth's spin with a global network of radio telescopes and satellites, will keep publishing the gap between atomic and rotational time. That record matters to geophysicists, because changes in day length offer clues about the core, ocean currents and ice loss.

What remains uncertain is how Earth's rotation will behave over the coming decades. Forecasts of day length are probabilistic, and the competing effects of core dynamics and melting ice make long-range predictions difficult. The new rule removes the urgency, but not the scientific interest.

The takeaway is calm. The planet's own changing spin pushed the world's timekeepers to act, and the result is a quieter clock for the technology people use every day. Nature World News will follow implementation as the May 2027 start date approaches.

What Readers Want to Know

What did timekeepers decide?

On Oct. 15, member states of the General Conference on Weights and Measures voted to stop adding leap seconds and let atomic time drift up to one hour from Earth's rotation.

When does the change take effect?

Continuous UTC without leap seconds begins May 20, 2027.

What is a negative leap second?

It would remove one second from clocks if Earth spins faster than atomic time. It has never been used, and experts feared it could disrupt computer systems.

Why is Earth spinning faster?

Changes inside Earth's core and other mass shifts can speed rotation by milliseconds, while tidal friction and melting ice slow it down over longer periods.

Do I need to change anything on my phone or computer?

No. Devices will continue to update time automatically.

When will a leap hour be needed?

Scientists estimate it may not be needed for more than 1,000 years.