A scientifically unprecedented development is redefining humanity’s understanding of time: scientists have confirmed that Earth is now rotating faster than ever recorded in modern history. Though the acceleration is too subtle to notice in daily life, it is shortening each day by milliseconds—prompting global timekeepers to prepare for a historic adjustment: subtracting a leap second from Coordinated Universal Time (UTC) by 2029.
For the first time since atomic timekeeping began in the 1960s, the world may have to delete time, not add it. This would mark a radical shift in the way humanity synchronises its clocks with the planet’s natural rhythm—highlighting the vulnerability of even the most precise human-made systems to Earth’s mysterious internal dynamics.
A day on Earth is generally understood to last 86,400 seconds, or 24 hours. But this has never been a fixed constant. Earth’s rotation fluctuates due to a complex web of geophysical, astronomical, and atmospheric factors. Since 2020, however, scientists have observed a consistent acceleration in Earth’s spin, making days shorter by fractions of milliseconds—an amount undetectable by humans but highly significant in atomic chronometry.
According to the International Earth Rotation and Reference Systems Service (IERS), headquartered in Washington D.C., this trend has continued into 2025, with record-breaking rotational speeds expected on July 9, July 22, and August 5 of this year. On August 5, the Earth is projected to complete a full rotation 1.51 milliseconds faster than the standard 24 hours.
This isn’t just an anomaly—it’s a potential paradigm shift. “If the trend persists,” experts warn, “the year 2029 could witness the first subtraction of a leap second in history to keep atomic time aligned with Earth’s increasingly fast rotation.”
Why the leap second matters
To understand the magnitude of this development, it’s essential to grasp the role of leap seconds in global timekeeping. Since 1972, timekeepers have periodically added leap seconds to UTC to account for Earth’s gradual rotational slowdown—a consequence of tidal friction, lunar drag, and internal geophysical processes.
Until now, the equation has always moved in one direction: Earth was slowing, so we added time.
Now, for the first time in the atomic age, Earth is speeding up, and the timekeepers may have to subtract a second—a decision with vast implications for precision systems that underpin everything from navigation satellites (GPS) to stock market transactions, military operations, and global communications networks.
“This is not just a technical correction,” a senior scientist at IERS explained. “It’s a moment that underscores how fluid time really is. The Earth has decided to spin faster—and now we must respond.”
What’s fueling this sudden acceleration? Scientists are still scrambling for definitive answers. Leonid Zotov, a prominent geophysicist from Moscow State University who co-authored a 2022 study on the phenomenon, admitted: “Nobody expected this. No existing model fully explains the speed-up.”
Theories under investigation include:
- Seismic activity redistributing Earth’s mass
- Glacial isostatic rebound, where land rises after the melting of ancient ice sheets
- Shifts in oceanic and atmospheric circulation
- Changes in Earth’s molten outer core, which may be exerting torque on the mantle
While the Moon has historically exerted a braking force on Earth’s spin through tidal interactions, these emerging forces appear to be working in reverse. “This is an ongoing mystery,” said a planetary physicist from NASA’s Jet Propulsion Laboratory. “And it highlights just how little we still understand about the deep interior of our own planet.”
How time has evolved and will continue to
To contextualize this change, scientists point out that Earth’s rotation has been slowing for billions of years. During the age of the dinosaurs, a day lasted about 23 hours. By the Bronze Age, it was just half a second shorter than it is today. Looking ahead, Earth is projected to have 25-hour days—but that will take over 200 million years to materialize.
Yet in this brief window from 2020 to 2025, a radical shift is underway.
These changes, while statistically small, are significant in a world where entire systems rely on nanosecond-level precision. For instance:
- Stock exchanges require atomic-level time for executing high-frequency trades.
- Telecommunication networks synchronize signals down to the microsecond.
- Global navigation satellite systems (GNSS) rely on stable time signatures to determine positions with metre-level accuracy.
Even a one-second mismatch can throw entire systems off balance—making the management of leap seconds a matter of global technological stability.
If Earth’s faster spin continues, timekeepers will face a delicate decision: subtract a leap second to realign UTC with Earth’s actual rotation. This has never been done before. All previous leap seconds—27 since 1972—have been added. A subtraction would require global coordination, extensive software updates, and real-time adjustments in mission-critical systems.
Fortunately, experts assure that the change will not affect everyday life. Your watch won’t stop ticking, and your phone will still function. But for scientists, engineers, and data architects, this is a monumental correction. “We are essentially editing time,” said a senior time scientist at the U.S. Naval Observatory. “It’s a rare but essential step to ensure we remain in sync with the spinning Earth.”
