Explained: The Elusive Leap Second

The things we do to keep the world running on time.

If you woke up yesterday feeling the slightest bit more refreshed, you can thank the leap second. If you woke up yesterday morning and your computer or favorite website (other than the Philly Post) had gone haywire—the single most terrifying computer-clock-based disaster in like 12 and a half years—you, too, can thank the leap second.

Of course, if you sneezed at 11:59:59 on June 30th, you completely missed the leap second, the only instance when a  “60” appears on a digital clock, your chance to “hop back,” to adapt a euphemism. (I spent my leap second playing Angry Birds and watching season 1 of Buffy the Vampire Slayer. It was like getting two extra seconds.)

But if you did miss it, don’t get too bent out of shape. Not because it was “only a second.” But because while this may be the first time most of us have even heard of a leap second, there have actually been 26 of them since 1972. That’s one every 1.54 years or so. So you’ll probably get your chance again. And they happen for the same reason leap years happen: As our time-keeping has gotten more sophisticated, we’ve had to tinker with our ancient notions of how long it took the sun to do a lap around the earth.

The reason this may be the first time many of us is actually hearing about the leap second is that back in the day, the only people who cared about keeping things quite so precise were the people following coordinated universal time (UTC). UTC is essentially time tracked by the number of times a cesium atom vibrates in one second—approximately 9,192,631,770 times). And the people who cared about it were scientists. And scientists in 1972 were not the cool scientists of today. They were nerds. Giant nerds.

But as the world’s gotten more linked together, by satellite and interwebs and GPS and the like, having all the world’s watches synced has become more than a heist film cliche. According to Dennis McCarthy of the U.S. Naval Observatory in Washington D.C. in this National Geographic News article, “In one billionth of a second, light travels about one foot [30 centimeters].”

Which is approximately 186,000 miles. Which is a bfd because navigation systems—y’know, how people do important things like land planes or crowdsource and create gaper delays—work based on the amount of time it takes a signal to bounce between satellites and receivers.

In some ways, the leap second is amazing. To be able to know to such precision what time it really is at any given point is truly an amazing accomplishment.

In other ways, the leap second is a gigantic bummer. We’re so close to getting it exactly right, and yet, we’re off every year or three.

But no matter how you look at the leap second (or if you decide to just ignore it), it was indeed nice of science to schedule it heading into what is shaping up to be for most American workers (if the vacation schedules in my office are any indication), that rarest of gifts, the Wednesday Independence Day five-day weekend. If you do the math, America’s 311 million or so citizens gained a combined 86,500 hours, perfect for making travel plans, catching an extra wink, or just getting a jump on the week’s work.

Five other tiny leap events I’d endorse:

• The Leap Sprinkle: It’s the last one that makes the difference.

• The Leap Heartbeat: Unscheduled, it’s quite a rush.

• The Leap Vacation Week: One year every five years or so, everyone gets an extra week of vacation.

• Leap Utley: Every couple of years we get a full season out of our star second baseman, and in that season, he can actually leap.

• The Leap Frog: I don’t really like to eat amphibians, but I might if I got a free one!