Earth completed its rotation on July 9 faster than usual, making it one of the shortest days in recorded history, scientists said Wednesday.
According to researchers, the planet spun roughly 1.3 to 1.6 milliseconds quicker than the standard 24-hour cycle. The rare acceleration is linked to the Moon’s shifting orbital path, particularly when it moves farther from Earth’s equator. This change exerts subtle gravitational effects that can temporarily increase the Earth’s spin rate.
Two additional days—July 22 and Aug. 5—are expected to show similar, though minor, reductions in day length.
While these changes are imperceptible to people, they have critical implications for systems that rely on precise timekeeping, such as atomic clocks, GPS satellites and global communication networks.
To keep Coordinated Universal Time, or UTC, aligned with Earth’s actual rotation, international timekeeping authorities may eventually need to implement a “negative leap second”—removing a second from the global clock. If needed, it would be the first time such an adjustment has ever been made. Scientists say this could happen as early as 2029, depending on how Earth’s spin rate evolves.
Experts emphasize that the recent shift poses no danger but offers insight into the complex dynamics of Earth’s core, atmosphere, oceans and interactions with celestial bodies. While the exact causes remain under investigation, researchers agree Earth is currently undergoing an unusually active period in its rotational behavior.