07-07-2025
Will we lose time on July 9? Midweek day losing time; here's why
Wednesday, July 9 is going to be one of this year's shortest days, but you probably won't be able to tell.
Here's why several milliseconds will be shaved off the clock on Wednesday, and when you can expect the phenomenon to occur again.
It takes roughly 86,400 seconds for Earth to complete a full rotation. The measuring of that rotation will cause an actual loss of time on Wednesday, July 9.
"86,400 seconds is another way of saying 24 hours. A millisecond is 0.001 seconds—considerably less than a blink of an eye, which lasts around 100 milliseconds," read Time and Date's website. "The only way to measure these tiny day-to-day variations in Earth's spin speed is with atomic clocks, which were introduced in the 1950s. The number of milliseconds above or below 86,400 seconds is known as length of day (LOD)."
The LOD has sped up over the decades, leaving to a shortening of days which will be most evident during three days in 2025.
"Until 2020, the shortest LOD ever recorded by atomic clocks was -1.05 ms. This means that Earth completed one rotation with respect to the Sun in 1.05 milliseconds less than 86,400 seconds," read Time and Date's explanation. "Since then, however, Earth has managed to shatter this old record every year by around half a millisecond. The shortest day of all was -1.66 ms on July 5, 2024.
"Earth is expected to get close to this again around July 9, July 22, and August 5."
From Quarks to Quasars explained Wednesday's loss of time in a lengthy Facebook post:
Moscow State University researcher Leonid Zotov said scientists haven't yet pinned down exactly what was causing the disparity in the time of Earth's rotation, but he expected Earth's rotation to regulate soon.
"In other words, we're not traveling back toward back toward the Mesozoic in terms of rotation," noted Popular Mechanics. "The planet will eventually continue its steady deceleration — this is, of course, its natural tendency, but surface changes like polar ice melt can also contribute to the Earth's rotation slowing down."
Damon C. Williams is a Philadelphia-based journalist reporting on trending topics across the Mid-Atlantic Region.
This article originally appeared on Earth's rotation shortens the day on July 9; what happens on Wednesday
