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Earth recorded its shortest day on record recently. And that could affect our clocks

Some days fly by faster than others, and it’s not a figment of your imagination.

According to the people who watch the world’s clocks for a living, June 29 this year was one of those days.

Earth completed one spin in 1.59 milliseconds less than 24 hours, making it the shortest day since the dawn of atomic clocks.

On July 26, Earth shaved 1.50 milliseconds off 24 hours.

If the trend gathers pace, timekeepers may need to create the first ever negative leap second to keep our clocks synchronized with the planet’s rotation.

So why is Earth spinning faster? And what impact will it have on the way we—and our computers—tell time?

First, let’s get up to speed with time.

Atomic and astronomical time

The time you, and your computer, live by is governed by Coordinated Universal Time, or UTC, set to your time zone.

UTC is mainly based on atomic time set by a network of 400 ultra-precise clocks around the world, including in Australia, that use the number of oscillations of a caesium atom.


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