By 2035, network-crashing leap seconds will be discontinued for at least a century

It’s not often that Facebook, Google, the USA, France, and Linus Torvalds can all agree on something, but they’ve done it this time.

On Friday, nearly all parties to the International Bureau of Weights and Measures (BIPM in its native French) approved Resolution 4, meaning that the leap second, a remarkably complex method of aligning the earth’s inconsistent rotation with atomic-precision timekeeping, will be phased out beginning in 2035. UTC, or Coordinated Universal Time, will function without them until the year 2135. At the time, it was unknown if there would be any leap seconds before that time, though it seems highly improbable that there would be.

The expectation is that within a century, time-focused scientists (metrologists) will have figured out how to make human-measured time coincide with Earth’s orbit around the Sun. Most people won’t even realise there’s a difference, even though in a century’s time the time difference could accumulate to an entire minute.

Dr. Patrizia Tavella, head of BIPM’s time department, told Agence France-Presse, “The connection between UTC and the rotation of the Earth is not lost, UTC remains related to Earth” (AFP).

Representatives from Russia voted against the resolution, and representatives from Belarus did not vote. Russia’s opposition, Tavella told AFP, was not “on principle,” but rather because Moscow wanted to postpone the elimination of the leap second until 2040. Russia’s GLONASS satellite positioning system has to be revised because it uses leap seconds. Tavella told AFP that the 2035 date was settled on as a compromise with other entities that wanted to bring forward the leap second removal.

Never again will system administrators, especially those at larger companies, know what disasters the next leap second will bring. Multiple hours of downtime occurred at businesses due to leap seconds in 2012 and 2017. These businesses included Reddit, Qantas, and Cloudflare. Many businesses adopted “leap smearing” to convert the microsecond difference caused by a leap second into a more uniform global time standard.

In the summer, Meta joined the chorus of critics of leap seconds. They have applied 27 leap seconds since their introduction in 1972, which is “enough for the next millennium,” as its engineers put it in a blog post. The possibility of a negative leap second was also brought up, which could introduce new forms of time-syncing torture to networks.

The International Telecommunication Union (ITU), which coordinates and disseminates UTC, may overrule the BIPM’s policy of ignoring leap minutes. The final say of the ITU is “the thing that makes us a little bit nervous,” as former BIPM time director Felicitas Arias told Nature. To counter this, Arias assured The New York Times that the BIPM and ITU negotiations would be successful.

In late 2023, right before the contract for ITU to maintain UTC time expires, the next decision-making conference of the ITU will take place in Dubai, United Arab Emirates. When that happens, it will probably be time for the leap second.