Claims circulating on social media have suggested that 5 August 2025 will be the shortest day of the year.
While it is among the shortest, scientific data indicates it is not the absolute shortest. According to timekeeping authorities, including the International Earth Rotation and Reference Systems Service (IERS) and the US Naval Observatory, four dates in 2025 will see days that are slightly shorter than the standard 24-hour cycle due to Earth’s accelerated rotation.
The duration differences, though measured in milliseconds, are significant in fields such as satellite communication, navigation systems, and atomic clock calibration.
The dates and their respective time differences are as follows:
- 9 July 2025: 1.23 milliseconds shorter
- 10 July 2025: 1.36 milliseconds shorter
- 22 July 2025: 1.34 milliseconds shorter
- 5 August 2025: 1.25 milliseconds shorter
Despite being imperceptible to the public, these minute changes are noteworthy for researchers and timekeeping institutions worldwide.
Why Is the Earth Rotating Faster?
The Earth’s rotation speed is not fixed and may vary due to several complex factors. One of the main contributors is the Moon’s position relative to Earth.
When the Moon moves further north or south of the equator, it can cause a slight increase in Earth’s rotational speed. Wind patterns, atmospheric changes, and the redistribution of the Earth’s mass due to melting ice caps also have an influence.
Additionally, scientists are investigating internal geophysical processes. Some have pointed to a possible deceleration in the movement of the Earth’s liquid core, which paradoxically may be contributing to an increase in the speed of the planet’s outer rotation.
However, there is no consensus on a definitive cause.
“No one expected this. The cause of this acceleration is unexplained,” said Dr Leonid Zotov, an expert on Earth’s rotation at Moscow State University, as quoted by EarthSky on Monday, 4 August 2025.
“Most scientists believe it is something within the Earth. Ocean and atmospheric models cannot explain this significant acceleration,” he added.
This acceleration has reversed the long-term trend of Earth’s rotation slowing due to the Moon’s gravitational pull.
The anomaly has led scientists to consider the possibility of introducing a negative leap second, a move that has never been implemented before and would present significant technical challenges for global timekeeping systems.
Will 5 August Be the Shortest Day?
According to National Geographic, the Earth’s rotation on 5 August 2025 is projected to be about 1.25 milliseconds faster than the standard 24-hour period. While this will make it one of the shortest days of the year, it will not be the shortest overall.
Similar occurrences have been recorded in recent years, with 22 July previously registering a day shortened by approximately 1.34 milliseconds. The acceleration in Earth’s rotation has become more noticeable since 2020, marking a deviation from long-established patterns.
Although these slight reductions in day length do not affect day-to-day life, they are closely monitored by scientists due to their implications for satellite operations, global positioning systems, and atomic timekeeping.
