Governments vote to retire the leap second by 2035

Time is running out for the controversial practice.

Massimo Ravera via Getty Images

The days of the leap second creating headaches for software engineers are coming to an end. On Friday, government representatives at the General Conference on Weights and Measures in Paris, France voted nearly unanimously to retire the practice of occasionally adding one second to official clocks (via The New York Times).

Introduced in 1972 as a way to adjust Coordinated Universal Time (UTC) to reconcile discrepancies that can come up between atomic time and observed solar time, the leap second has been the bane of tech companies for decades. In 2012, for instance, Reddit was down for about 40 minutes when the addition of a leap second that year confused the company’s servers. More recently, Cloudflare saw part of its DNS services affected due to a time change in 2016.

Companies like Facebook parent Meta employ a technique called “smearing” to avoid outages whenever the International Earth Rotation and Reference Systems Service adjusts UTC to add a leap second. Earlier this year, the social media giant published a blog post calling for an end to the practice. “Every leap second is a major source of pain for people who manage hardware infrastructures,” Meta said at the time. Part of the push to eliminate the leap second has come as a way to preserve UTC as the world’s official international time.

With this week’s vote, dignitaries from the US, Canada and France called for the practice to end before 2035. Russia voted against the proposal. In the past, the country has sought to delay the demise of the leap second because GLONASS, its global positioning system, incorporates the adjustment – the Global Position System (GPS) operated by the US does not. Felicitas Arias, the former director of the Time Department at the International Bureau of Weights and Measures told Nature the decision may force Russia to launch new satellites.

There’s still another organization that needs to weigh in on the matter before software engineers can breathe a sigh of relief. The International Telecommunications Union, the group responsible for transmitting universal time, will vote on the issue next year. If it moves forward with “Resolution D,” metrologists and astronomers will have until at least 2135 to figure out how to reconcile the atomic and astronomical time scales.

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