Leap seconds cause chaos for computers — so Meta wants to get rid of them

Leap seconds cause chaos for computers — so Meta wants to get rid of them

Since 1972 there have been 27 leap seconds: additional seconds added to the world’s common clock — Coordinated Universal Time or UTC — to account for changes in the Earth’s rate of rotation. Our traditional definition of time was a fraction the length of the sunday. However, the Earth’s spin rate is irregular, slowing down and speeding up depending on different factors, so solar time and universal times tend to drift apart. So, in order to compensate, we add leap seconds. And this really confuses computers.

Just imagine that you are a computer. You have a very clear sense of time. You know that there are 24 hours in a day, 60 minutes in an hour, and 60 seconds in a minute: all neat and tidy. Then, on some random day as you await the coming dawn, you watch with horror as your internal clock ticks over from 23:59:59 to the previously-undreamt-of time of 23:59:60. Naturally, you panic. Maybe you crash a little, just to calm your nerves. As a result, you take down some of the biggest websites in the world. Everyone gets mad at you.

This isn’t a comedy situation. When a leap second was added in 2012, it caused substantial outages for sites like Foursquare, Reddit, LinkedIn, and Yelp. By 2015, when the next leap second was due, engineers had mostly learned their lessons, but there were still some glitches. Ditto 2016. As Linux creator Linus Torvalds put it: “Almost every time we have a leap second, we find something. It’s really annoying, because it’s a classic case of code that is basically never run, and thus not tested by users under their normal conditions.”

This is why social media conglomerate Meta wants to get rid of the leap second. In a blog post published yesterday, the company’s engineering team outlined their argument against adding leap seconds, saying it’s an adjustment that “mainly benefits scientists and astronomers” (as it allows them to make observations of celestial bodies using UTC). Meta says that this benefit is now less significant than ever and overshadowed by the chaos leap seconds create in the technology world.

“Introducing new leap seconds is a risky practice that does more harm than good, and we believe it is time to introduce new technologies to replace it,” says the company.

According to a report from CNET, Meta is not alone in this, and this campaign has attracted support from other tech giants like Google, Microsoft, and Amazon, as well as heavy-hitters in the international measurement community, like the US National Institute of Standards and Technology (NIST) and France’s Bureau International de Poids et Mesures (BIPM).

But without leap seconds, what happens to coordinated universal time? Is it okay to let the time drift out of line with solar? Well, there are options, as Meta points out. The smear second alternative is another. This means that digital clocks are slowed down over a longer time period in order to add the required leap second — effectively spreading the needed leap second across several hours.

However, there are problems with this method too. Smear seconds can be calculated in many ways, especially when it comes to the time period that you are using to allocate the “extra” time. And, as there’s no single, centralized method of tracking time across the world’s many digital systems, this means alternate methods could also create confusion and outages.

Meta isn’t proposing any one solution to the problem. It’s only saying that there needs to be one. This is an issue that other organisations are currently examining. The next big milestone will be a report on the matter commissioned by the UN’s International Telecommunication Union or ITU in 2015. That’s due out in 2023. Because you really can’t rush this sort of thing.

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