Earth’s rotation speeds up mysteriously again, making August 5 one of the shortest days

Three such days have been identified in 2025: July 9, July 22 and August 5. Each of these will be shorter by around 1.2 to 1.3 milliseconds. The shortest solar day ever was on July 5, 2024, when Earth spun 1.66 milliseconds faster than the full 24 hours.

Earth’s faster rotation is confusing scientists. For decades, the planet had been gradually slowing. Now, without a clear explanation, it is speeding up again.

How does the Moon influence Earth’s rotation?

The Moon contributes to the long-term rotation of Earth. As it revolves around the planet, it slowly moves away. This motion induces a tidal pull that slows down the rotation of Earth, which results in longer days in the long run.

The position of the Moon can also bring about temporary alterations. Its declination or angle with respect to Earth's equator, can impact tides and consequently the planet's rotation. Scientists believe this may explain the shorter days in July and August this year.

What could be causing the long-term change?

While the Moon affects short-term wobbles, deeper causes are suspected for the recent acceleration. One possible reason is changes in Earth’s liquid core.

Some researchers suggest the core may be rotating slower, which causes the outer layers to spin faster. Others point to climate factors, though no direct link with global warming has been confirmed yet.

Even though this change won’t be felt in daily life, it has consequences for timekeeping. If the trend continues, experts may need to add a negative leap second by 2029. That has never been done before.

For now, August 5 will pass like any other day but just a little quicker.