A Day Shorter Than Usual

On July 9, 2025, the Earth made headlines by spinning a bit faster than our usual 24-hour schedule, resulting in a day that was approximately 1.3 to 1.6 milliseconds shorter. While this may sound trivial, it marked the shortest day recorded since accurate records began.

More Short Days Ahead!

And it’s not just a one-off occurrence! Scientists predict that two more brief days are on the horizon—July 22 and August 5—thanks in part to lunar influences.

Why Is Earth Spinning Faster?

The Earth’s rotation isn’t a perfectly steady cadence. Although we standardize a day to 24 hours, fluctuations do happen, caused by both internal forces like tectonic activity and external factors like the moon’s gravitational pull.

Interestingly, Earth's rotation is gradually slowing down over centuries due to tidal friction—essentially, the moon’s gravitational pull on our oceans is functioning like a brake, adding around 2 milliseconds to each day every century. However, in the short term, days can actually become shorter, and that's exactly what we’ve observed on July 9.

The Moon’s Influence

On July 9, the moon reached its maximum declination, which means it was positioned farthest from Earth’s equator. This unique positioning alters gravitational pull, slightly modifying Earth’s axial wobble and leading to a surge in rotational speed. Similar effects are anticipated for the upcoming short days on July 22 and August 5.

Precision Monitoring of Earth’s Rotation

Thanks to advancements in technology, scientists have monitored the planet’s rotation with millisecond precision using atomic clocks since the 1960s. Coordinated global timekeeping began in 1972, allowing experts to track minute variations in Earth’s rotational pace by comparing Universal Time 1 with International Atomic Time (TAI). According to the International Earth Rotation and Reference Systems Service (IERS), July 9, 2025, holds the title for the shortest day ever recorded.

Could We Lose a Second?

Absolutely! This could lead to a historic first. Typically, when Earth's rotation slows, scientists introduce a "leap second" to Coordinated Universal Time (UTC) every few years to keep civil time synced with Earth’s actual spin. The last adjustment was made in 2016.

However, with the current trend of increasing speed, the opposite challenge looms—removing a second. This would require implementing a 'negative leap second,' a concept never realized until now.

Some scientists speculate that if Earth's rotation continues to accelerate by just a few milliseconds annually, we might face the necessity of this adjustment around 2029. Exciting—and unprecedented—times are ahead!