Informopedia Explains: the vote in Versailles that quietly changed how humanity keeps time — and why your grandchildren’s grandchildren still won’t see the fix it promised.
On the last day of 2016, something strange happened to the world’s clocks. At 23:59:59 UTC, time did not roll over to midnight. Instead, clocks read 23:59:60 — a sixty-first second, inserted into the minute — and only then did 2017 begin. It was the 27th time since 1972 that timekeepers had slipped an extra second into the world’s official time.
Last week, they voted to never do it again.
On October 15, 2026, the General Conference on Weights and Measures — the diplomatic body that decides how humanity measures everything from the kilogram to the second — adopted a resolution abolishing the leap second. In its place: a system that lets official time drift from Earth’s rotation by up to a full hour before anyone has to act. Scientists are calling it the leap hour.
It is one of the strangest, most consequential votes you’ve never heard of. Here’s what it means.
What the leap second was — and why it existed
Coordinated Universal Time, UTC, is the world’s official time — the basis for everything from your phone’s clock to airline schedules. It is kept by atomic clocks, which measure time by counting the vibrations of cesium atoms: 9,192,631,770 oscillations of a cesium-133 atom equals one second, by international definition since 1967. These clocks are astonishingly stable.
The problem is that Earth is not. Our planet’s rotation wobbles and slows, mostly because of the Moon’s gravitational pull dragging on the oceans — tidal friction that lengthens the day by roughly 1.7 milliseconds every century. Earthquakes shove it the other way: the 2004 Indian Ocean earthquake shortened the day by about 2.68 microseconds. Glacial rebound, shifting winds, the sloshing of the molten core — the planet’s spin is a restless, irregular thing.
So the atomic second and the solar day slowly disagree. Since 1972, the International Bureau of Weights and Measures (BIPM) — the intergovernmental organization in Sèvres, France, that maintains UTC — has inserted leap seconds to keep official time within 0.9 seconds of time measured by Earth’s rotation. The decision falls to the International Earth Rotation and Reference Systems Service (IERS), which announces a leap second about six months in advance. Twenty-seven were added. The last was December 31, 2016.
The second that crashed the internet
Adding a second sounds trivial. In practice it has been a menace. Computers expect time to flow in one direction, continuously and predictably. A minute with 61 seconds — or, worse, one with 59 — breaks that assumption in ways that cascade.
When a leap second was added on June 30, 2012, Reddit went down. So did LinkedIn and Yelp. Qantas’s booking system failed, stranding passengers. The problem was buried deep in the Linux kernel: a bug in how certain systems handled the extra second sent processors into a spiral, consuming all available CPU. When the 2016 leap second arrived, customers of the internet infrastructure company Cloudflare experienced outages and delays after its servers failed to handle the insertion properly.
Tech giants responded with workarounds. Google invented the “leap smear” — stretching the extra second across a full 24 hours so its servers never see a 61-second minute. Meta did something similar. But every company smeared differently, quietly fracturing the idea of a single global time. And in 2022, Meta’s engineers published a blog post calling for the leap second’s abolition, describing it as a “major source of pain.” “It’s always been a problem,” Judah Levine, a former physicist in the Time and Frequency Division of the US National Institute of Standards and Technology (NIST), told Scientific American.
Then came the twist that concentrated everyone’s mind: Earth started spinning faster. Since the mid-2010s, the planet’s rotation has been accelerating — June 29, 2022 was the shortest day ever measured. Timekeepers faced the prospect of the first negative leap second: deleting a second instead of adding one, perhaps as early as 2029.
No one has ever tested that. “It’s never happened before, and therefore the software for that has never been tested,” Darryl Veitch, who leads the Timing Lab at the University of Technology Sydney, told the Australian Broadcasting Corporation. Engineers described it as a mini Y2K. “Avoiding negative leap seconds is a very big driver” of the decision, said Nick Stamatakos, head of the Earth Orientation Department at the US Naval Observatory, which manages the timing behind America’s GPS satellites.
Who decided — and what they actually voted for
The vote happened at the 28th meeting of the CGPM in Versailles, the same body that redefined the kilogram in 2018. It caps roughly thirty years of argument. “After 30 years of debates, we are ready,” said Noël Dimarcq, a senior scientist at France’s National Center for Scientific Research and president of the BIPM’s Consultative Committee for Time and Frequency, just before the vote.
Resolution 5 does not cut the link between atomic time and the turning planet. It loosens it. From World Metrology Day — May 20 — 2027, UTC will be allowed to drift up to one hour from astronomical time before anyone must act. Georgette Macdonald of Canada’s National Research Council said the decision “will ensure the continuity and relevance of UTC for centuries to come.”
Christian Bizouard, director of the IERS Earth Orientation Center in France, put the philosophy more bluntly: “It’s kind of a philosophical discussion, because if a leap hour happens, it won’t be for a very, very long time. What we are doing is pushing back the decision.”
So when do we get the leap hour?
Almost certainly never — at least not anyone reading this. At the current rate of drift, accumulating a full hour of difference between UTC and Earth’s rotation would take more than a thousand years. There is no scheduled date and no agreed procedure for inserting it. The resolution effectively hands the problem to a civilization that may measure time in ways we can’t imagine.
The BIPM will keep measuring and publishing the gap between the two time scales for the people who still need Earth’s exact orientation — astronomers, satellite navigators, deep-space missions. Everyone else just gets continuous time, ticking forward without interruption.
The same Versailles meeting also started work on two longer-term projects that tell you where timekeeping is headed: a time standard for the Moon, and a redefinition of the second itself, replacing cesium with optical atomic clocks that are thousands of times more precise.
Why this matters
Nothing on your wristwatch changes. Your phone won’t notice. But the vote marks something bigger: the moment humanity admitted that its machines’ needs now outweigh the romance of keeping our clocks tied to the turning Earth.
For three centuries, time was astronomical — the swing of a pendulum, the transit of a star. In 1967 we redefined the second around the atom, and we’ve been papering over the difference with leap seconds ever since. The leap hour is the quiet confession that the paper patches are over. Civil time is now, officially, atomic time. The planet can wobble all it likes; our clocks will no longer flinch.
What happens next
Engineers get what they wanted: a predictable, continuous UTC, no more 23:59:60, no mini-Y2K lurking in the calendar. The transition takes effect in May 2027, and the leap second joins the growing museum of technologies that the internet outgrew.
But keep one irony in mind. The whole scheme was invented to keep noon aligned with the sun overhead. A thousand years from now, if nobody ever inserts the leap hour, noon by the clock will drift toward what used to be called 1 p.m. — and the only people who will care are astronomers pointing telescopes at a sky that never agreed to run on atomic time in the first place.
