Scientists predict August 5th will be one of the shortest days of the year due to changes in the Earth’s core and atmospheric influences. This phenomenon results from the core slowing down, causing the rest of the planet to speed up. The core’s spin affects the Earth’s rotation over periods of 10 years to hundreds of years.
According to the International Earth Rotation and Reference System Service and the U.S. Naval Observatory, August 5th is predicted to be 1.34 milliseconds shorter than 24 hours. This variation is imperceptible to humans but can impact atomic clocks and systems reliant on precise timekeeping.
The predictions come after a series of short days this year, with July 11 being the most recent example. However, previous predictions have not always come true, as seen in July’s data which showed only 0.87 milliseconds were shaved off from the expected time. The shortest day recorded so far was July 5, 2024, coming in 1.66 milliseconds short.
The Earth’s rotation is also influenced by atmospheric forces, particularly during the summer of the Northern Hemisphere. Forces caused by the moon can further affect the rotation rate. On a geologic timescale, the Earth has been slowing down due to its core slowing down, with the rotation taking half an hour less 70 million years ago.
While this short day may not be noticeable for most people, it could pose problems for scientists tracking atomic clocks and other timekeeping systems. Discrepancies of even a small amount can affect computers, servers, GPS signals, and networks that rely on accurate times.
Source: https://eu.usatoday.com/story/news/nation/2025/08/04/august-5-short-day-2025/85517066007