Earth to Experience Three of the Shortest Days in Summer 2025 as Rotation Speeds Up
In an unusual twist, scientists say Earth will experience three significantly shorter days this summer due to an unexpected acceleration in its rotation.
Typically, Earth completes one full rotation every 86,400 seconds — the equivalent of 24 hours. However, on July 9, July 22, and August 5, the planet’s spin will shave off as much as 1.51 milliseconds per day, according to Popular Mechanics. These dates are expected to rank among the shortest days since 2020, according to the International Earth Rotation and Reference Systems Service.
Researchers attribute the timing of this anomaly to the Moon’s position being furthest from the equator on those specific days, which subtly affects Earth’s rotational speed.
The shortest day recorded in recent history occurred on July 5, 2024, which was 1.66 milliseconds shorter than average. Despite the increased precision in monitoring Earth’s movements, experts still cannot fully explain the source of this acceleration.
“This came as a surprise,” said Leonid Zotov, an Earth rotation specialist at Moscow State University, in an interview with TimeandDate.com. “Most scientists think it originates from inside the Earth, as ocean and atmospheric patterns don’t account for the extent of the acceleration.”
The trend has raised serious questions for timekeeping authorities. A study published in Nature suggests that if the acceleration continues, a “negative leap second” may be required by 2029 — a historic first — to recalibrate official global time.
“This is unprecedented and significant,” said study author Duncan Agnew, a geophysicist at the Scripps Institution of Oceanography. “It’s not going to cause a catastrophe, but it’s another reminder that we’re living in a very unusual period.”
Historically, the length of a day on Earth has varied. During the Bronze Age, for instance, a full rotation took closer to 23 hours.
This story was originally published by the New York Post and republished with permission.
