Earth is set to mark Wednesday, July 9, as the shortest day ever recorded, with similar short days anticipated on July 22 and August 5, 2025. Scientists attribute this phenomenon to the Moon’s current position, which is influencing Earth’s rotation and causing it to spin slightly faster, resulting in days that are marginally shorter than usual.
A report by Live Science explains that the Moon’s position is expected to reduce the length of each of these days by between 1.3 and 1.51 milliseconds than the normal day.
July 22 and August 5 are projected to be comparably short, according to a New York Post report citing data from the International Earth Rotation and Reference Systems Service (IERS).
The IERS, which oversees global timekeeping, will eventually need to introduce a “negative leap second” to adjust for the string of shortened days – marking the first time such a correction will be implemented.
This adjustment is currently expected in 2029.
“This is an unprecedented situation and a big deal,” NY Post quoted Duncan Agnew, a geophysicist at the Scripps Institution of Oceanography at the University of California, San Diego, as saying.
“It’s not a huge change in the Earth’s rotation that’s going to lead to some catastrophe or anything, but it is something notable,” he added.
Earth's rotation explained
{{/usCountry}}“It’s not a huge change in the Earth’s rotation that’s going to lead to some catastrophe or anything, but it is something notable,” he added.
Earth's rotation explained
{{/usCountry}}A day on Earth is defined as the time the planet takes to complete one full rotation on its axis – roughly 86,400 seconds, or 24 hours.
However, this rotation is not constant and can be influenced by various factors such as the positions of the Sun and Moon, shifts in Earth’s magnetic field, and the distribution of the planet’s mass.
Historically, Earth’s rotation has been gradually slowing down, which has caused the length of days to increase over time. Scientists estimate that between 1 to 2 billion years ago, a single day lasted only about 19 hours.
This was likely because the Moon was much closer to Earth, exerting a stronger gravitational pull and making the planet spin faster.
As the Moon has slowly moved farther away, Earth’s rotation has decelerated, resulting in longer days on average.
Yet, in recent years, researchers have noticed irregularities in this trend. In 2020, for instance, scientists observed that Earth was rotating faster than at any point since precise measurements began in the 1970s.
The fastest rotation recorded was on July 5, 2024, when Earth completed its spin 1.66 milliseconds quicker than the usual 24 hours, according to timeanddate.com.
What is changing on July 9, 22 and August 5?
On July 9, July 22, and August 5, 2025, the Moon will reach its farthest position from Earth’s equator, altering how its gravitational pull influences the planet’s axis.
Picture Earth like a spinning top – if you try to spin it by gripping it at the center, it won’t rotate as quickly as it would if you spun it from the ends.
When the Moon shifts closer to Earth's poles instead of hovering near the equator, its gravitational influence changes. This positioning causes the planet to spin a bit faster, which shortens the length of each day.