Have you looked at your 2024 calendar?
February is one day longer this year.
“The time it takes for the Earth to go around the sun is about 365.25 days,” said Angela Speck, Professor and Department Chair for Physics and Astronomy at UTSA.
Yet, our man-made calendar measures one year as exactly 365 days.
“So what you get is 365 days for three years, and then you add one day on the fourth year so that then you’re back where you started,” said Speck.
In other words, that one-fourth of a day we don’t acknowledge most years is accounted for in one full day every four years.
Well, almost every four years. (We’ll get into that in just a bit).
While you may not be an astronomy expert like Professor Speck, you probably know that as the Earth orbits around the sun our planet is also spinning.
But get this: the axis the Earth spins on, so to speak, is spinning itself.
Think of a spinning top. While the top itself is rotating fast, it’s also moving in a circular path as it spins.
That secondary rotation is much slower than the spin of the top itself, much like how the Earth is rotating.
It’s why one year is not actually one full trip around the sun.
“It’s a little bit less than that, about 20 minutes,” said Speck. “This has to do with keeping the seasons on track. That axis is actually ever so slightly spinning around. It’s very slow.”
It takes 26,000 years for the axis of the Earth to make one full orbit.
“But over the course of one year, it’s moved just a little bit,” Speck said. “And so what happens is as you are going around the sun, you get back to the same position just ever so slightly before you’ve done one full orbit.”
Keeping seasons in check
Without a Leap Year, that misalignment would cause the seasons to shift a tiny bit every year.
Things may not change much difference in 365 days, but that movement would add up over a longer period of time.
“We would have spring in June instead of March. We would have winter in September and so on. And so over time, the calendar would get messed up,” said Elizabeth Hasseler, Assistant Professor of History at Texas A&M University-San Antonio.
Leap Day dates back to the ancient Roman Period when Emperor Julius Caesar switched from using a lunar calendar to a solar calendar.
But Leap Day wasn’t always on February 29.
“For several hundred years, what they would do is they would create a second February 24th,” Hasseler said. “So you would have February 23rd, February 24th, February 24th, and then February 25th.”
Yeah, that got confusing.
“So by the end of the Middle Ages, they started to shift over to using February 29th rather than a second February 24th,” Hasseler said.
Caesar’s calendar started running into another problem: holidays were off.
“By the 16th century, the Catholic Church was running into the issue that Easter, one of the most important holidays in the Christian calendar, was being celebrated too early in the year because of this discrepancy,” Hasseler said.
The seasons weren’t falling at the correct time of year, which meant that Easter was off since its date is determined by the Spring Equinox.
So, buh-bye Julian Calendar.
In 1582, the Julian Calendar was replaced by the Gregorian Calendar, which was created by Pope Gregory XII.
It is still the calendar we use today and it includes a leap year every four years. Almost.
Here’s the rule:
Leap Year happens every four years unless the year is divisible by 100 — with one exception. Leap Year can happen on a year divisible by 100 if it is also divisible by 400.
A complicated combination of math and science led to those rules.
“This helps adjust for the very slight discrepancy between the length of our day and the length of an astronomical day,” said Speck.
The Leap Day Lady
There’s something else a little complicated about Leap Day for those born on Feb. 29.
But The Leap Day Lady is here to help.
“My name is Raenell Dawn, Leap Day Lady,” she told KSAT.
Raenell will turn 16 at 64 this year (and she has the T-shirt to prove it).
That’s to say she will be 64 years old on Feb. 29, but her ‘leap age’ is 16.
In 1988, Dawn, who lives in Oregon, started a birthday club for people born on leap day.
What began as a club connecting its members via meet-ups and snail mail has now morphed into LeapYearDay.com, ‘the Honor Society of Leap Year Day Babies.’
“It’s the most important date on the calendar! Not the most important day, the most important date,” Dawn said.
Over the years, members of that society started noticing that they ran into similar issues.
Take a driver’s license, for example.
“I was told when I moved to my state, ‘you need to choose February 28th or March 1st because there’s no February 29th. It’s not on the calendar. It’s not in my computer,’” Dawn said.
Think about signing up for something online. You’re frequently asked to enter your birthday.
“Well, we put our birth date in and this little window pops up and says, ‘Please enter a valid date,’” she said. “And so my attention turned toward that to be on a mission to correct the incorrections that need correcting.”
“You may quote me,” she told KSAT with a smile.
The Leap Day Lady contacts companies and suggests they add February 29 as an option.
She says technology is changing to accommodate that.
“I’m not saving the world. I’m just one of those people who is okay to speak up about things,” Dawn said. “It’s a quadrennial window I get to climb in.”
And when that window rolls around, some people born on Leap Day go all out.
“We have leap day babies turning 13 and 15, and they’re doing their bar mitzvahs, and their quinceañeras and things like that again, as adults,” said Dawn. “How fun!”
Why not? It only comes around every four years. Almost.