Feb. 29 2012 12:00 AM

How Feb. 29 keeps the year humming



A good repairman is hard to find.

Every four years, the calendar starts to shudder and creep out of place, like a dryer with a bad belt. Wait too long to fix it and the damn thing will creep across the floor.

On schedule, every four years, Feb. 29 pulls up in a van, grabs a wrench and sets the year humming, with no fuss or fanfare.

Where does this quiet fixer come from? How does he do it? What, exactly, is he fixing?

Don’t jump in the van so fast. Have a beer, Leap Year. Tell us your story.

To explain the invisible dance of time, Dr. David Batch, director of the Abrams Planetarium at MSU, said it’s necessary to “back up a little.”

“When the planets were formed … ,” he began.

Better get a six-pack.

Before clouds of gas clumped together into the Sun and the planets, they were nebulous, if not unruly. Gravity walked into the solar schoolyard like a nun with a ruler and whipped things into order.

“Take something like a nebula, that’s spread out and large, and let gravity do its thing,” Batch explained. “It’ll shrink down. Things will spin. As more and more material builds up in the center, the spin becomes greater.”

Over time, the sun, the planets, the asteroids and whatnot settled into a routine. But they all have different sizes and distances from each other, so they ended up with different spins, at different speeds, on different scales.

The large-scale wheeling of the Earth around the sun — the first basis for our year — isn’t connected in any way with the small-scale spin of the Earth on its axis — the first basis for our day. They don’t even write to each other.

“We’re talking about the rotation of the Earth versus the revolution of the Earth,” Batch explained. “There’s no connection. There’s no reason there would be an equal number of days in a year.” 

That’s where Leap Year comes in.

“The way I think about it, it’s an attempt to match up the length of time it takes the Earth to go around the sun with an even number of days,” Batch said.

My grasp of the concept was nebulous, even with Batch’s help, until I realized that his name reminded me of cookies. I pictured the universe as a dysfunctional cookie factory where Earth years are tubes of cookie dough that hold 365 and one-fourth cookies each. The day worker in charge of extruding the dough refuses to change the cookie size, insisting that a cookie must as big as the day is long.

So every year, one-fourth of an extra cookie plops down onto the conveyor belt. What if the Health Department shows up?

Along comes Leap Year every four years, wearing sanitary gloves, to gather the four blobs into a full-sized cookie. Every fourth batch (small “b”) has 366 cookies. Nothing left over.

What would happen if that correction weren’t made? After 500 years, there would be a blob of dough big enough to make 125 cookies oozing all over the machinery.

To bring it back to the calendar, if there were no leap days, the calendar would lag 125 days behind the solar year’s familiar cycle of the seasons in 500 years. That’s about four months. You didn’t plant your beans in January? Too bad. No harvest for you in May, or whenever the harvest is these days.

To get a sense of how little discrepancies add up, try turning on your car radio and finding a song with a beat that matches the windshield wipers. After three or four wipes — the Leap Year interval — the match is still close. After 10 wipes, you start to hear a lag. Another minute or two and it’s obvious there was never any relationship at all.

It turns out that if you don’t insert leap days, the year’s round of familiar events, from monsoon to planting time to harvest to ratings sweeps week, will cycle through the entire calendar in 1,460 years.

That’s the predicament the Romans found themselves in the time of Julius Caesar. Over the years, the vernal equinox, the first day of spring, had drifted into June. Caesar took a rare minute from his far-flung campaigns to hammer the calendar back into shape.

It was time to “intercalate,” or insert “extra” days in the calendar to make it march in step with the thing it was supposed to measure — the “real” year, with its seasons and feast days and clearance sales.

The Romans turned to the Egyptians for advice, and not just because of the gravitational attraction between Caesar and Cleopatra. The Egyptians know their solar years. Unlike civilizations that used lunar calendars, like the Greeks, the Egyptians relied on annual rhythms, most of them linked to the all-important flooding cycle of the Nile.

A wise man named Sosigenes advised Caesar to insert a day every four years. Egyptians already knew that the day was slightly less than 365 and a quarter days long (later nailed down to 365.242199 days), but the four-year leaping scheme was close enough for Roman government work.

After the Julian reforms, the year was still 11 minutes, 14 seconds too long, but that would cause much less trouble than six hours. “It’s just a longer time before it has to be corrected,” Batch said. “But most of us are happy with that amount of discrepancy.”

In the late 16th century, Pope Gregory III spearheaded the last (maybe) adjustment to the system. The years 1600, 2000 and 2400 would stay leap years, but all other “century” years would go back to 365 days. Gregory also wiped 10 days out of the year to make up for the calendar’s gradual drift since Caesar’s day.

It took a long time for the Gregorian reforms to soak in around the world, especially in English-speaking countries where the pope wasn’t very popular. That’s why George Washington has two birthdays, Feb. 11 (when he celebrated it) and Feb. 22 (when we celebrate it, now that England and America begrudgingly adopted the Gregorian calendar).

In Britain, the Gregorian reforms stirred up street riots over “stolen days.” Those kinds of fights seem distant now.

We don’t even use the Sun and planets to tell time anymore. Nowadays, a year is measured as 290,091,200,400,000,000 oscillations of cesium. That kind of accuracy is too perfect for the wobbles and hiccups of the real Earth, buffeted by tiny gravitational nudges from Jupiter and the other planets. Every now and then, the International Earth Rotation Service adds or subtracts a “leap second” to the year to make super-accurate human-made clocks line up with eccentric nature. It may come as welcome news for people who want to do some more leaping after Feb. 29 that a leap second is due to be added June 30, 2012.

There’s something reassuring about the way we take all this in stride. I asked April Clobes, vice president and chief operating officer at the MSU Federal Credit Union, how Leap Year affects the financial world.

“I don’t think I have anything to add to your story, as the software is all programmed to handle the additional day,” she wrote back calmly. Michael Diebold, a spokesman for the Roman Catholic Diocese of Lansing, and Mandalyn Starski of MSU’s Pagan student society Green Spiral, both told me Leap Year is a non-event for their groups. Astrologer Lynn Crandall told me the same thing.

Maybe it’s Leap Year’s sheer insignificance that makes it worth a salute. For centuries, the calendar has been a means of control. The Roman calendar, with its endless feast days, kept citizens mindful of the imperial order. The Christian inheritors of that calendar filled it with feasts and saints’ days that regulated ritual and behavior through the year. In the consumer culture of modern America, the same calendar has become a rigid round of binge buying, yoked to many of those same holidays.

Against that backdrop, Leap Year, the quiet fixer, is an oasis of cooperation and practicality. It may be the only sane day of the year.