Earth's faster spin may cause shorter days, scientists warn — should you be concerned

Scientists have discovered that Earth is rotating slightly faster than usual, making our days shorter by a few milliseconds. While the change is minimal, it has significant implications for global timekeeping systems. Typically, leap seconds are added to atomic clocks to match Earth’s slower rotation. However, if this faster spin continues, experts predict that by 2029, we may need to subtract a leap second for the first time in history. This would mark a major milestone in how we align human-made timekeeping with natural planetary rhythms, highlighting how even time is influenced by Earth’s subtle yet dynamic changes.

How Earth's day length has evolved over millions of years

The Earth takes approximately 86,400 seconds to complete one full rotation, which equals one day. However, this duration is not perfectly constant. Various natural phenomena from gravitational forces to internal geophysical changes cause slight variations in how fast Earth spins.Historically, Earth’s rotation has gradually slowed down. For example, during the era of the dinosaurs, days lasted only about 23 hours. By the Bronze Age, they had lengthened but were still about half a second shorter than today. In the long term, Earth may experience 25-hour days, but scientists estimate that will take another 200 million years.

Earth’s rotation is changing: What it means for the length of a day

Since 2020, Earth has been spinning slightly faster, a trend that has surprised scientists. According to the International Earth Rotation and Reference Systems Service (IERS), based in Washington, D.C., this acceleration has continued steadily.The result? Shorter days by just a few milliseconds. If this trend persists, experts say we might need to remove a leap second from Coordinated Universal Time (UTC) by 2029. This would be the first time in history that a leap second is subtracted rather than added. A leap second is a one-second adjustment added periodically to atomic clocks to align them with Earth's irregular rotation. Since Earth's spin is not perfectly synchronized with atomic time, leap seconds help bridge that gap.So far, leap seconds have only been added to account for the Earth’s slowing rotation. However, if Earth continues to spin faster, we may have to remove a second from atomic time for the first time ever. This adjustment would ensure that clocks continue to match Earth's actual rotation.

Shortest days of 2025 expected in July and August, say scientists

According to timeanddate.com, the trend of shorter days is expected to continue into 2025. Scientists have pinpointed three specific dates when Earth’s spin is expected to be fastest:

According to USA Today reports, on August 5, the length of a day could be 1.51 milliseconds shorter than the standard 24 hours—a noticeable deviation in scientific terms, even if humans won’t perceive it.

What’s causing Earth’s faster spin

The exact reason behind the recent acceleration remains unclear. Scientists are currently exploring several possibilities:

However, Leonid Zotov, a researcher at Moscow State University, told timeanddate.com, “Nobody expected this.” He co-authored a 2022 study on the topic, but he admitted that no current model fully explains the phenomenon. While changes in the oceans and atmosphere may contribute to fluctuations in Earth’s spin, they likely aren't strong enough to account for this significant acceleration. Some researchers believe that movement within Earth’s molten outer core could be influencing rotational speed.

Scientists reassure: Leap second removal is routine and won’t impact daily life

Despite the unusual findings, scientists are not alarmed. While it is rare for Earth’s rotation to speed up, such fluctuations are not unprecedented. Over centuries, the planet still trends toward a gradual slowdown.The potential removal of a leap second in 2029 is simply a technical correction—one that helps keep atomic clocks in sync with Earth's rotation. It will not affect daily life, devices, or global operations. However, it is a fascinating reminder that even something as reliable as time is influenced by complex natural forces beneath our feet.Also Read | Buck Moon 2025: When and where to watch July’s Full Moon of the summer with top viewing tips