The International Earth Rotation and Reference Systems Service (IERS) announced on Thursday there will be no leap second added to 2024.

The standards keeping body established that there was not enough difference between time as measured based on atomic clocks (UTC) and time as measured by the Earth's natural rotation (UT1) to warrant making a ripple in time.

UT1 varies thanks to phenomena like gravitational interactions with the Moon and Sun, and geological activities such as earthquakes which alter the speed of Earth's rotation.

UTC and UT1 therefore might not always match. The IERS maintains a maximum value of ±0.9 seconds by which the two can vary.

If that limit is exceeded, various applications that sync UTC and UT1 can strike trouble as time stamps don't align. That's when a leap second is thrown in. If you're interested in the current difference between UTC and UT1, you can check it out here.

Earth's rotation slowed in recent decades, creating a need for 27 leap seconds introduced between 1972 and 2016. Our planet's spin has sped up a little since - which is why we've not had a leap second added for a few years.

Leap seconds are added to UTC time at the end of December or June, and announced six months before their implementation.

While a leap second has never been subtracted, doing so is a theoretical possibility and may one day be warranted.

Leap seconds are more than timekeeping trivia - computers must keep up with very precise changes to the way humanity measures time.

Last time a leap second was added, Cloudflare suffered a limited service interruption and Linux servers choked. Systems that rely on precise timing - such as GPS and financial trading platforms - can be affected too.

Meta's engineering team therefore proposed doing away with leap seconds back in 2022. It's an interesting development on many levels - not least that the social network reckons it has enough power to sway a global problem-solving phenomenon.

But adding leap seconds is a known problem, even if annoying and resource-sucking. As at least one blogger has noted: "No one, or almost no one, is ready for a negative leap second."

It's extremely likely that Meta will get its way and the leap second will become a thing of the past. Back in November 2022 The Bureau International des Poids et Mesures (BIPM) declared 2035 as the year in which the concept will be binned.

The plan is to replace it with a "new maximum value for the difference (UT1-UTC) that will ensure the continuity of UTC for at least a century." ®

https://www.theregister.com//2024/07/05/iers_decrees_no_leap_second/