Researchers say Earth will rotate slightly faster in the coming weeks, shortening some days by about 1.3 to 1.51 milliseconds. July 9 was also a slightly shorter day. The same is expected for July 22 and August 5 because the Moon’s position will change Earth’s rotation.
A day on Earth lasts 24 hours, or 86,400 seconds. That’s how long it takes our planet to complete a full rotation on its axis. However, that rotation is influenced by a number of factors, including the positions of the Sun and Moon, changes in Earth’s magnetic field, and the redistribution of mass on Earth’s surface.
Since Earth’s formation, its rotation has gradually slowed, lengthening days. Researchers have found that 1 to 2 billion years ago, a day on Earth lasted only 19 hours. That shorter day is likely related to the Moon being closer to Earth back then, which increased the Moon’s gravitational pull and made our planet spin faster.
Since then, as the Moon has drifted away, the average length of a day has increased. But in recent years, scientists have observed shifts in Earth’s rotation. In 2020, they reported that Earth was spinning faster than at any time since observations began in the 1970s.
On July 5, 2024, scientists recorded the shortest day in the history of observations. According to data from timeanddate.com, that day was 1.66 milliseconds shorter than 24 hours.
On July 22 and August 5, 2025, the Moon will be at its maximum distance from Earth’s equator, which will change the Moon’s gravitational effect on Earth’s axis. (The same occurred on July 9.)
Imagine Earth as a spinning top. If you hold a top by the middle and spin it, it will rotate more slowly than if you hold it at the top and bottom and spin it.
As the Moon moves toward the poles, Earth’s rotation speeds up, making the day shorter than usual.
Human Impact and Other Factors
These fluctuations are expected. However, recent studies have shown that human activity is also changing Earth’s rotation. NASA calculated that the redistribution of ice and groundwater linked to the climate crisis increased the length of Earth’s day by 1.33 milliseconds per century between 2000 and 2018.
Earth’s rotation can also be altered by specific events. For instance, the 2011 earthquake in Japan shortened the length of the day by 1.8 microseconds. Richard Holme, a geophysicist at the University of Liverpool, said seasonal changes also affect Earth’s rotation.
“In the Northern Hemisphere, there is more land than in the Southern Hemisphere. In the summer, trees in the north leaf out, which moves mass toward the surface—farther from Earth’s axis of rotation,” Holme explained to Live Science. The rotation speed of any spinning body depends on how its mass is distributed. As Earth’s mass moves farther from the core in summer, its rotation slows and days get longer, Holme said.
Of course, our clocks still show 24 hours. We don’t feel this difference. Holme said a shift in time zones would only be necessary if the day lengthened by 900 milliseconds (0.9 seconds).
