What are the odds of being born on leap day? Slim. So slim that leap baby Adam Piekarski decided to get his 7-year-old daughter to do the math with him to prove to her how special he is.

"Everyone that I’ve met that’s been born on a leap year seems special," he said. "I personally think they think differently and they see differently."

Normally, the chance of being born on any given day is 1 in 365. But for leap babies, it's four times that, plus an extra day. That comes out to 1 in 1,461. So only 0.07 percent of the world’s population shares a birthday with Adam — assuming birthdays are uniformly distributed throughout the year.

Adam, who works on an oil pipeline in Ohio, technically has had more birthdays than his daughter. On February 29, he will mark his ninth real birthday. (In more conventional terms, he’s turning 36.)

Adam is one of the Vox followers who responded to my call on Twitter for leap year babies. Over the past week, I spoke with eight of them. I wanted to know about the rituals, inconveniences, and delights that come along with a birthday that vanishes three out of every four years. There are many.

When do leap year babies celebrate their birthdays?

This is an existential question for leap babies. The community is divided into "28thers" and "1sters," as one reader, Phil Haney, told me.

Haney, a writer for Break.com in Los Angeles, is a 1ster. "My mother always told me that I was born ‘the day after the 28th.’" He said. "I wasn't here on the 28th, so it makes more sense to celebrate on March 1."

Shannon Esposito, a fourth-grade teacher outside Chicago, is an avowed 28ther. "I have always, always celebrated on February 28. To me, it’s always been a February birthday," she said. "I am not a March baby!"

Some try to split the difference by celebrating the moment the clock strikes 12 between the two days. Lidia Urbina, a master’s student in Switzerland, says that’s the tactic her friends often say they’ll take – but most years, they just forget.

Others don’t see a reason why they have to pick sides. Alex Clifton, an enrollment counselor in Kentucky, says she cuts her losses by celebrating on both days. (Clifton is turning 6 – or 24 – but she strikes me as wise beyond her years.)

Still others let the date float around the calendar. I got the sense that since leap year babies’ birthdays don’t exist most years, it’s almost as though they feel unmoored from the specific date they actually celebrate.

"I used to try and keep it in February, but most often I celebrated on the weekend," Piekarski told me. "Now I’m grown up with kids, so I try to celebrate within the month."

Is there pressure to have a blowout celebration every four years when the real date rolls around?

Definitely. "It's like the Olympics, a presidential election, and my birthday every four years," Haney said. That puts a lot of pressure on him to go out and do something really big.

Ashley Eden, a staffer for Sen. Dianne Feinstein on Capitol Hill, told me her parents set an over-the-top expectation that was hard to meet. When she turned 4, her first real birthday, her parents rented a pony. She and her friends spent hours taking mini horseback rides through the backyard. For a later birthday, when she was 16, her parents sent a limo to pick her up from school.

"They wanted to make sure I saw it as a cool and special thing, rather than a bummer that I had a birthday every four years," she said.

Another reader, Susan Peck, wrote in with what I can only imagine is a more unique ritual. "I am about to celebrate my 14th actual birthday," she wrote in an email. "I'll be singing the song from Pirates of Penzance: ‘a paradox, a paradox, a most ingenious paradox! Ha ha ha ha ha ha ha ha, a paradox!’" (The Pirates of Penzance is a comic opera written by Gilbert and Sullivan whose main character is also a leap year baby.) This raised many more questions, but Peck did not respond to any of my follow-up inquiries.

But Espasito noted that despite the impulse to "go big," leap day lands on a Monday this year, and she’ll probably end up celebrating the weekend before. She’s looking forward to leap day 2020, though, which lands on a Saturday.

Does everyone make the joke that you’re a quarter of your actual age?

Are you turning 32, or 8? That’s the question leap year babies can’t avoid on their actual birthdays. Eden says she gets a lot of coloring books and crayons on her "real" birthday. People routinely tell Urbina that she looks old for her age (24, or 6.) And Espasito says the joke causes her fourth-grade students endless amusement – "we’re older than our teacher, blah blah blah," she puts it.

"I sometimes feel bad for the people that make the joke because they're trying to be nice, and they really think they are being original," Urbina said. "But it's actually a bit annoying."

Mike Guardabascio, the high school sports editor for the Long Beach Press-Telegram in California, says the joke’s corniness doesn’t discriminate. "You could be talking to the guy down the street, or you could be talking to an astrophysicist," he said. "When you tell someone that you were born on February 29, the immediate response is, ‘So are you, like, 6 years old?’" (For the record, Guardabascio is turning 8, or 32.)

What happens when leap year babies turn 21?

For all the hype around 21st birthdays, most of the people I interviewed didn’t have much of a problem with the precise date they chose. That meant, again in nearly every case, that these leap day babies all tried their luck on the 28th.

"Before my 21st birthday, I spent an exorbitant amount of time on Wikipedia to figure out when I could go out for a drink," Clifton told me.

Technically, bouncers should not let 21-year-old leap year babies into bars until March 1, but when Clifton tried her luck on the 28th, she didn’t meet resistance. Same goes with Espasito, who rushed to buy beer on the 28th.

Haney didn’t have a problem, either, until months after his 21st birthday. But one night, he went to a bar in his hometown, and the bouncer threatened to confiscate his license over the birth date listed.

Evidently, the bouncer hadn’t ever heard of leap year.

"He was positive it was a fake ID and was real proud of himself that he had caught me," he said. "He thought I was the idiot for having a fake ID that didn't even have a real birthdate on it."

Haney recounted trying frantically to explain the concept of leap year to the bouncer, while the bouncer started bending his ID in half. Thankfully, a waitress noticed the ruckus and rushed over to straighten things out.

Do forms or official documents ever pose a problem?

In the United States, a person’s birthday during common years, or non-leap years, is likely March 1.

Piekarski says, and others echo, that renewing his license is a reliable nuisance. Department of Motor Vehicle employees, who likely glaze over after typing so many dates, routinely print forms saying he must renew his license on 2/29/2017, a date that obviously doesn’t exist.

Espasito has even seen DMV workers try to print IDs with the wrong birthdate listed. "I always get flagged, I always have to produce my birth certificate," she said.

Web forms frequently cause problems, too. Often, drop-down boxes simply don’t have more than 28 days listed under February. In those cases, most people just fudge it and hope for the best.

But the stakes are higher on Facebook. Unlike many less sophisticated websites, Facebook does recognize February 29 as a valid birth date. But for years, the social network didn’t know how to adapt during non-leap years.

On February 28, it would alert users that their friend’s birthday was coming up the next day. But on March 1 ... nothing.

"That’s how I knew who my real friends were," Haney said.

Most leap year babies say Facebook has since fixed the glitch, and, per the government’s example, it defaults to March 1.

Do leap day babies share a particular bond?

For the most part, it seems as though leap day babies find it mildly amusing to compare notes with others in their exclusive club. Most of the leap year babies I spoke with said they knew one or two others, though several groups exist to unite people more broadly.

The pool of birthdays is so small, Clifton said, that she recognizes every name on a list of famous people who share her birthday. Ann Lee, the founder of the Shakers, is one. Ja Rule, an outmoded rapper, is another.

"I cannot identify a single Ja Rule song, but we share a birthday," she said.

The exercise can get tiresome. The birthday is so rare that whenever someone learns of a leap day baby’s birthday, they feel compelled to connect the dots with any other leap day babies they know.

"People go to a pretty far extent to tell me anyone they know who was also born on leap year," Eden said. "'Oh, my brother’s second-grade teacher was born on leap year!’"

What are the biggest perks of having a leap year birthday?

Each leap day, businesses do offer an array of specials for people born on the 29th. This year, specials include free food, free birthday parties, and even free travel.

During the last leap day, Guardabascio told me he found so many food specials – one at IHOP, another at Papa John’s pizza – that he and his wife ate three meals out, for free. Haney said an upscale cupcake shop in his neighborhood, Sprinkles, gave him a free box of cupcakes. ("Worth $40!" he emphasized.)

The deals for 29thers are so lucrative that ahead of this year, Guardabascio created a Google alert for "leap day birthday free."

But on non-leap years, leap year babies do run the risk of missing normal birthday perks, like a free cup of coffee at Starbucks. Most said that cashiers are generous about such things, allowing them to redeem birthday perks the days before or after. But Eden says she doesn’t even run the risk.

"When they ask for your birthday, I always put the 28th, because if you get a freebie, I don’t want to miss it," she said.

Are there more intangible benefits, too?

I posed this question to every leap year baby I interviewed – what they liked most about their birthday. While many did bring up freebies, there was also a larger sense that their birthday marks something special about them.

Some say it’s their go-to "fun fact" during icebreakers. Others say it simply helps people remember their birthday.

Guardabascio, who spoke to me while driving with his baby in the back seat, said he enjoys his birthday mostly because it serves as a potent reminder of just how much his life has changed.

"The time before this one, we didn’t have any kids. The time before that, we were in college," he said of his wife and him. "It’s an interesting way to mark the passage of time."