July 22nd is one of the shortest days in history

Tuesday, July 22, 2025, is one of the shortest days in recorded history, 1.34 milliseconds shorter than the standard 24-hour day. This imperceptible variation, measurable only by atomic clocks, reflects a new pattern of our planet that began in 2020, according to metrologist Leonid Zotov of Time and Date.

We're used to thinking that our planet rotates at a constant speed and that every day is exactly the same, but measurements with extremely precise clocks like atomic clocks since 1973 have revealed that this isn't exactly the case. Indeed, there are tiny fluctuations between one day and the next, changes due to tides, earthquakes, the movement of the Moon, and many other small events that can affect the Earth's rotation. It's even believed that about 1 billion years ago, a day lasted just 19 hours, and over time, the gradual retreat of the Moon slowed the Earth to its current 24 hours, or 86,400 seconds.

With the advent of atomic clocks, it was discovered that each day exhibits small differences, and the shortest ever measured to date were June 30, 2022 (which lasted 1.59 milliseconds less) and July 5, 2024 (which lasted 1.66 milliseconds less). But by observing these variations, researchers discovered that they were quite limited until 2020, after which the planet has repeatedly broken its own records, as if accelerating. These trends were partly predictable, so much so that at the beginning of the year, experts predicted new possible speed records for July 9 (which recorded a rotation time of 1.36 milliseconds less than 24 hours), July 22, and August 5.

Predictions indicate that on July 22, the Earth will complete its rotation 1.34 milliseconds early, making it the second shortest day of 2025, while August 5 is expected to be about 1.25 milliseconds shorter than usual.