One of the shortest days on record just occurred.
For reasons that no one has been able to discern, the Earth has been spinning faster since roughly 2020, after decades of slowing down (starting in the mid-1970s). The vast majority of us won’t notice the effects, but scientists do — especially since that increase in speed resulted in August 5, 2025, being one of the shortest days ever recorded.
That recent Tuesday was 1.25 milliseconds shorter than a usual day, which may seem infinitesimal, but is actually quite a landmark event. There’s a distinction between a solar day, which is how long it takes Earth to rotate on its axis relative to the sun (exactly 24 hours), and sidereal days, which are the planet’s true rotation period relative to distant stars (23 hours, 56 minutes, and 4.1 seconds); in this case, both were slightly shorter than usual.
Three other dates in 2025 were notably short: July 9 (1.23 milliseconds less than 24 hours), July 10 (1.36 milliseconds less), and July 22 (1.34 milliseconds less). The shortest day ever recorded was July 5, 2024, which was 1.66 milliseconds under the usual 24 hours. Short-term fluctuations in Earth’s rotation speed are caused by the moon’s gravitational effects on our humble planet, but the long-term increase in speed in recent years is less understood. Should it continue for four more years, however, a “leap second” may be subtracted from a single day in 2029.
he North and South Poles don’t have official time zones.
If you’ve ever argued that time is merely a human construct, you may enjoy learning about time zones at the Earth’s poles. As science writer Katie Weeman put it in Scientific American, the poles are simultaneously in “all of Earth’s time zones and none of them,” and they have no official time zone.
That’s because all 24 longitude lines (which mark the time zones) converge in these spots, making the zones essentially meaningless once they reach the North Pole and South Pole. Since both poles are generally uninhabited, there’s also no real need for an official time. Antarctica’s research stations navigate this problem by observing either the local time of their home country or that of the nation nearest them, whereas the North Pole has no permanent research stations.
Michael Nordine is a writer and editor living in Denver. A native Angeleno, he has two cats and wishes he had more.
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