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Earth Just Set A New Record For The Shortest Day

Somehow the shortest days are never in January. 


Dr. Alfredo Carpineti

Senior Staff Writer & Space Correspondent

clockJul 29 2022, 15:26 UTC
The earth in space with the sun shining its light on the right hand side
At least it was a weekday. Image credit: Iryna Store/

Earth just set a record for the shortest day. Not that it was appreciable by us, but hey, at least it was a weekday. 

The International Earth Rotation and Reference Systems Service measured Wednesday, June 29, 2022, was 159 milliseconds shorter than 24 full hours. That's the shortest day since scientists started using atomic clocks to measure Earth's rotational speed.


In general, the Earth spins once every 24 hours. However, the length of the day has variability due to several factors that can make it longer or shorter. The tidal forces between the Earth and the Moon are actually stretching the day and generally making it longer. Every 100 years or so Earth takes an extra couple of milliseconds to complete a spin. The internal motion of the planet and of the atmosphere also shifts the length, as does the motion of our satellites

But, over the last several years it seems like the length of the day is getting shorter. Earth has broken lots of speed records since 2020. In fact, in 2020, it had 28 of its shortest days recorded since the 1960s. Nobody knows for sure why this is happening but one suggestion is related to changes to the axis of rotation, which has not been wobbling as much over the last five years.

Understanding complex motions of the planet, especially if they are related to long-term cycles might take a while but fortunately, most of the effects of these variations are negligible. If there is too much or too little difference accumulated after months or even years, a leap second might get added to the official time and date.


This very useful tool to keep time has recently come under fire from internet giants Facebook, Google, Amazon, and Microsoft as the introduction of an extra second can occasionally disrupt software. 

The last leap second was added on December 31, 2016. There is no expectation of adding an extra second in 2022.   

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