by NEW YORK (AP) – Leap Year. The calendar is a delight for the math nerds among us. So how did it all start and why?
Take a look at some of the numbers, history and lore behind the phenomenon every four years that adds a 29th day to February.
BY THE NUMBERS
The math is mind boggling in a secular way and down to fractions of days and minutes. Sometimes there is even a second jump, but there is no hullabaloo when that happens.
What you do know is that the leap year exists, in large part, to keep the months in sync with annual events, including the equinox and solstice, according to the Jet Propulsion Laboratory at the California Institute of Technology.
It is a correction to counteract the fact that the Earth’s orbit is not exactly 365 days a year. The trip takes about six hours longer than that, NASA says.
Contrary to what people believe, however, we do not read every four years. If a leap day were added every four years, the calendar would be 44 minutes longer, according to the National Air and Space Museum.
Later, on a yet-to-be-coming calendar (we’ll get to it), years divisible by 100 would be ruled out from following the four-year leap day rule unless they’re also divisible by 400, the JPL notes. In the last 500 years, there was no leap day in 1700, 1800 and 1900, but there was one in 2000. In the next 500 years, if the practice is continued, there will be no leap day in 2100, 2200, 2300 and 2500.
Still with us?
The next leap years are 2028, 2032 and 2036.
WHAT DO YOU DO WITHOUT A LEAP DAY?
Finally, nothing is good in terms of when major events fall, when farmers plant and how the seasons align with the sun and moon.
“Without leap years, after a few hundred years we’ll have summer in November,” said Younas Khan, a physics instructor at the University of Alabama at Birmingham. “Christmas will be in the summer. There will be no snow. It won’t feel like Christmas.”
WHO BROUGHT THE MOST TO THE BED YEAR?
The short answer: It evolved.
Ancient civilizations used the cosmos to plan their lives, and there are calendars dating back to the Bronze Age. They were based on the phases of the moon or the sun, as are various calendars today. They were usually “lunisolar,” using both.
Now jump forward to the Roman Empire and Julius Caesar. He was dealing with a major seasonal influx of calendars used in his neck of the woods. They dealt badly with adding a three-month stream. He was also launching a wide variety of calendars starting a wide variety of routes in the vast Roman Empire.
He introduced his Julian calendar in 46 BCE. It had one sun and a year counting at 365.25 days, so once every four years an extra day was added. Before that, the Romans counted a year at 355 days, at least for a while.
But still, under Julius, there was a current. There were too many leap years! The solar year is not exactly 365.25 days! It is 365,242 days, said Nick Eakes, astronomy educator at the Morehead Planetarium and Science Center at the University of North Carolina in Chapel Hill.
Thomas Palaima, a professor of classics at the University of Texas at Austin, said the ancients added periods of time to a year to reflect variations in the lunar and solar cycles. The Athenian calendar, he said, was used in the fourth, fifth and sixth centuries with 12 lunar months.
That didn’t work for seasonal religious rituals. As a result of the current problem, an extra month was periodically “swapped” to realign lunar and solar cycles, Palaima said.
The Julian calendar was 0.0078 days (11 minutes and 14 seconds) longer than the tropical year, and thus gradually accumulated errors in keeping time, according to NASA. But stability has increased, Palaima said.
The Julian calendar was the model used by the Western world for centuries. Enter Pope Gregory XIII, who calibrates further. His Gregorian calendar came into force in the late 16th century. It is still in use today and, obviously, it is not perfect or there would be no need for a leap year. But it was a big improvement, reducing the current to one second.
Why did he come in? Well, Easter. It was coming later in the year over time, and he was concerned that events related to Easter such as Pentecost might clash with pagan festivals. The Pope wanted Easter to stay in the spring.
He abolished several extra accumulated days on the Julian calendar and modified the leap day rules. It was Pope Gregory and his advisers who came up with the real math of when there should or shouldn’t be a leap year.
“If the solar year was a perfect 365.25, we wouldn’t have to worry about the complicated math involved,” Eakes said.
WHAT ARE THE YEARS OF BED AND MARRIAGE?
It is strange that Leap Day comes with a legend about women asking men about marriage. It was mostly innocuous fun, but it came with the sting of reinforcing gender roles.
European folklore is distant. One story puts forward the idea of women proposing in fifth-century Ireland, with St. Bride asking St. Patrick to allow women to ask men to marry them, according to historian Katherine Parkin in a 2012 paper in the Journal of Family History .
No one really knows where it started.
In 1904, syndicated columnist Elizabeth Meriwether Gilmer, aka Dorothy Dix, summed up the tradition this way: “Of course people will say … that women’s leap year prerogatives, like most of their freedoms, are nothing but a joke sparkling.”
The pre-Sadie Hawkins tradition, however serious or tongue-in-cheek, could empower women but perpetuate stereotypes. The proposals were supposed to happen via postcard, but many such cards turned the tables and made fun of women instead.
Advertising has won the leap year marriage game. A 1916 advertisement from the American Industrial Bank and Trust Co. read the following: “As this New Year’s Day passes, we suggest to every girl that she plans for her father to open a savings account in her name in our own bank.”
There was no breath of independence for women because of leap day.
SHOULD YOU LIKE THE LEAPLINGS?
Someone born in a leap year on leap day is certainly a talking point. But it can be kind of a pain in terms of paperwork. Some governments and others that required filling out forms and stating birthdays came in to confirm which date whistleblowers used for things like driver’s licenses, whether it was February 28th or March 1st.
Technology has made it much easier for baby boomers to chart their milestones on February 29, although there may be glitches with health systems, insurance policies and with businesses and other organizations that haven’t entered that date.
There are about 5 million people in the world who share the leap birthday out of about 8 billion people on the planet. Shelley Dean, 23, of Seattle, Washington, chooses a rosy outlook about being a jumper. Growing up, she had a normal birthday party every year, but an extra special one when the leap years were over. Since, as an adult, she marks that non-leap period between February 28 and March 1 with a “whew.”
This year is different.
“It will be the first birthday I’ve celebrated with my family in eight years, which is really exciting, because my last leap day was on the other side of the country in New York for college,” she said. . “It’s a really big year.”
