Record-breaking short days could speed up leap second debate

Meta recently joined the ranks of the tech giants in calling for an end to the leap second, the fascinatingly complex way people explain tiny changes in the timing of the Earth’s rotation. The owner of Facebook and Instagram is adding to a chorus that has grown over the years, and the debate could come to a head at a global conference in 2023, or even sooner if Earth continues to experience record short days.

Facebook, like many big tech companies, is tired of trying to keep its global network of servers in sync with leap seconds that add 0.1 to 0.9 seconds to Coordinated Universal Time (UTC) every so many years. Since 1972, 27 leap seconds have been added. In a post on the engineering blog Meta, Oleg Obleukhov and Ahmad Byagowi say 27 is good enough for non-solar scientists — “enough for the next millennium.”

International timekeeping bodies add leap seconds at unpredictable intervals because the things that cause them—the braking effect of tides on rotation, the position of the moon, the distribution of ice caps on mountaintops, the flow of the mantle, earthquakes—are unpredictable. When the Earth’s speed differs too much from atomic timekeeping, the International Earth Rotation and Reference Systems Service (IERS) requires a leap second.

At midnight on the appointed day, the clock ticks from 23:59:59 to 23:59:60 to 00:00:00. This unusual average timestamp drives coordinated systems crazy. The leap second in 2012 was ahead of Reddit, Gawker and Australian airline Qantas. Cloudflare took the hit in New Year 2017 (and detailed why). Since then, many technologies have prepared for the next leap second by “smearing the leap “or using microsecond slowdowns during the long, global server-friendly time window until midnight.

Meta engineers point out that while every leap second has been positive so far, negative leap seconds — the kind that computer systems couldn’t easily “smear out”— could be due to “a change in the Earth’s rotation pattern.”This is far from empty speculation.

The Earth recently experienced a record short day on June 29, 1.59 milliseconds short of the 24-hour norm. This is part of a general acceleration trend. The second shortest day was July 19, 2020, 1.47 milliseconds short, to July 26, 2022, 1.50 milliseconds short, one day after the Meta vs. Leap Second was posted.

Leonid Zotov from Moscow State University. M.V. Lomonosov said timeanddate that, in his opinion, the cause may be the uneven movement of the geographic poles of the Earth. But Zotov also believes there is a “70 percent chance”that a negative leap second will not be needed, at least this year.

Arguments against leap seconds have been accumulating since the crashes caused by the last two (with the occasional bizarre dissent). The last time a formal decision was discussed was in 2015 at the World Radiocommunication Conference in Geneva. The International Telecommunication Union (ITU) has postponed the decision to 2023. The next big timekeepers talk will take place at the end of 2023 in Dubai. United Arab Emirates, when the contract delegating UTC timekeeping to the ITU expires.

The Meta’s call to action might not be the first, but it could end up being a great moment.