The Leap Second Is About to Rattle the Internet. But There’s a Plot to Kill It.
The Qantas Airways computers started crashing just after midnight. A few hours later, as passengers started flying home from weekend getaways, there were long delays in Brisbane, Perth, and Melbourne, and the computers still didn’t work. Qantas flight attendants were forced to check passengers in by hand.
That Sunday morning in July 2012 was a disaster for Amadeus IT Group, the Spanish company responsible for the software that had computer screens flickering at Qantas kiosks. But it wasn’t entirely the company’s fault. Most of the blame lay with an obscure decades-old timing standard for the UNIX operating system, a standard fashioned by well-intentioned astronomer time lords. They were working for an international standards body, a precursor of the International Telecommunications Union, which today officially tells clock-keepers how to tell the rest of the world what time it is. Back in 1972, they decided to insert the occasional leap-second into Coordinated Universal Time (UTC), the standard most of the world uses to set wristwatches.
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We’ve had 25 of these leap seconds since then, and we’re about to get our 26th. This week, the modern time lords announced that the next leap second will arrive at 11:59 p.m. and 60 seconds on June 30. That has some computer experts worried. Amadeus wasn’t the only company to go glitchy during the last leap second. Reddit, Foursquare, and Yelp all blew up thanks to the leap second and the way it messed with the underlying Linux operating system, which is based on UNIX.
The trouble is that even as they use the leap second, UNIX and Linux define a day as something that is unvarying in length. “If a leap second happens, the operating system must somehow prevent the applications from knowing that it’s going on while still handling all the business of an operating system,” says Steve Allen, a programmer with California’s Lick Observatory. He likens it to the problem facing the HAL 9000, the fictional onboard computer in Stanley Kubrick’s 2001: A Space Odyssey, which loses its mind after it is programmed to lie. “All the problems that crop up are, in a metaphorical sense, the HAL 9000 problem. You have told your computer to lie. I wonder what it will do,” he says.
People watch and photograph a clock in Tamura, Fukushima Prefecture, Japan, showing the time of 8:59:60, at the moment when a leap second was inserted, on July 1, 2012. (The Yomiuri Shimbun/Associated Press)
The Linux kernel folks aren’t expecting any major issues when July 1 comes around, but the situation is unpredictable. Back in 2012, Linux creator Linus Torvalds told us: “Almost every time we have a leap second, we find something.” And this time around, there will be problems again. Torvalds doesn’t think they’ll be as widespread as they were three years ago, but they’re largely unavoidable. The “reason problems happen in this space is because it’s obviously rare and special, and testing for it in one circumstance then might miss some other situation,” he says.
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As a result, some insiders are trying to abolish the leap second, in favor of a more reliable system. But they may or may not succeed. Yes, we already have atomic clocks that don’t need leap seconds, and some standard time systems already use these clocks. GPS has worked off of atomic clocks for decades, leap second free. But some believe UNIX and Linux, its ultra-popular clone, should continue to get their time from the leap-second-friendly UTC standard. They want man and machine to remain in line.
You can think of the whole mess as a kind of cosmic struggle between machines, which consider a day to be 86,400 seconds, and humans, who think of a day as one spin of planet Earth. For thousands of years, one rotation of the earth was indeed the best way of measuring 86,400 seconds, but it turns out this is an imperfect method.
The moon’s gravitational pull on the earth’s water messes with things. So do earthquakes. In fact, there are many factors that can slow down or speed up the Earth’s spin, much like an ice skater extending and pulling back her arms.
If the world moved completely to atomic clocks, then after tens of thousands of years, noon would fall in the middle of the night. And long after that, spring would be the season, here in the U.S., that starts in November.
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Switching to something like the GPS system seems like an obvious way around this. Let the computers have their crazy time and leave UTC for human wristwatches. But things aren’t quite so simple. Some think abandoning UTC would lead to more time-translation problems. And because so many computers are already hard-coded to use the UTC standard, weaning them from it would be a big and nasty piece of coding work. “It would just cause other problems instead,” Torvalds says. “Many worse problems.”
With the next leap second looming, some of our current time lords are looking to abolish the whole idea at the next meeting of the International Telecommunications Union, the group responsible for UTC. The leap second question has been openly debated for 15 years, but this November, it will come to a head at the 2015 World Radiocommunication Conference in Geneva, according to Wayne Whyte, a NASA program manager who chairs the group that’s studying whether to drop the leap second.
Will it get passed? Nobody knows for sure, but people who follow the time war say that some members of the ITU really don’t like the idea. “It’s a really complicated issue,” says Marek Kukula, the public astronomer with the Royal Observatory Greenwich. “Some of the contributing factors are cultural and emotional,” he says.
Kukula wouldn’t be surprised to see the debate tabled for another decade or two. “My impression is that they’re not desperate to come to a conclusion,” he says. “And, in their position, I totally understand how they feel.”
None of this will be much use to Udo Seidel, over at Amadeus Software. The ITU meeting doesn’t happen until months after the June leap second, so he’s quietly building out a set of test tools that allow system administrators to simulate the leap-second effect and see if everything crashes.
Seidel was working at Amadeus back in 2012 when it systems crashed, so he’s probably one of the first people you’d expect to call for is abolition. But when I ask him what he thinks, he grows thoughtful on the phone. Whimsical, even.
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We should keep the earth and its computers in alignment he tells me. To him, it just feels like the right thing to do. And besides, he’s a technologist. “If we cannot manage to make our systems handle a leap second,” he says, “then we have bigger problems.”
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