The twenty-ninth day of February (usually) comes only once every four years (except for years which can be divided by 100 and cannot be divided by 400). As the only date in the calendar that doesn't occur in every year, it has some comedic potential, especially when it's someone's birthday: Any event happening on someone's "Xth birthday" won't actually happen until he's 4 times X years old. People whose birthday falls on Leap Year's Day are known as "leapers" (not like that) or "leaplings."
This can be a hassle if said character wants to celebrate their birthday every year. One way to do this is to celebrate it on February 28 or March 1 so technically they'd still 'age' normally. This is what legal jurisdictions will do for the purposes of determining when someone reaches the age of majority, though whether it's the day before or after depends: the UK and Hong Kong consider March 1 as the day for leapers, while New Zealand and Taiwan will use February 28.
- Touya Kinomoto from Cardcaptor Sakura has his birthday on February 29. His mother always added it to her date calendars.
- In Karin, Kenta was born on 29 Feb 1988. Elda threatens to wipe his memory back to his fourth birthday, not realizing that she is doing so on his fourth birthday.
- King of Prism: Shin and Louis' birthdays are both on February 29, and the fact that their birthdays are on the same day makes it a Significant Birth Date.
- In Mobile Suit Gundam ZZ, Haman formally declares the founding of the Neo Zeon movement on February 29, UC 0088. Fans have used this to try and determine at what point the calendar transitioned from AD to UC.
- According to the Databooks, Kabuto Yakushi from Naruto was born on this day.
- Pandaman from One Piece, a Easter Egg character that appears hidden in nearly every chapter was given this birthday in the SBS Vol. 85.
- A gag in Otaku no Musume-san revolves around Kanau's birthday being on February 29.
- The Ouran High School Host Club manga explains that senior student Honey looks younger than the freshman students since he was born on February 29.
- Tokyo Ghoul: Big Bad Kichimura Washuu was born on this day.
- Cain Dressel from Valvrave the Liberator is given this birthday in the series site. Fitting since Cain is Older Than He Looks.
- Before the Crisis on Infinite Earths, Superman's birthday was February 29. Yes, really. To be more exact, it was Feb. 29 on Earth on the day he was born on Krypton. He celebrates the day the Kents found him separately, as Clark Kent's birthday.
- In The Golden Age of Comic Books, Feb. 29 was also Captain Marvel's birthday. (Hey, maybe he and Superman were separated at birth!) In a manner of speaking, they were. Golden Age Marvel Family writer Otto Binder eventually went to work for DC on the Superman titles in the Silver Age, coming up with many of the familiar Superman mythos elements (Krypto the Superdog, the Phantom Zone, Supergirl, etc.). This might explain some of the tone/elements of Silver Age Superman stories...
- It used to be that Leap Day was the day on which women could propose to men, instead of the other way around as was the informal custom of the time. Carol Ferris tried to take advantage of this in an issue of Green Lantern.
- Irish folklore has this as the day Saint Bridget struck a deal with Saint Patrick to allow women to propose to men. This is the premise of the 2010 Amy Adams film Leap Year.
- Weirdly, this trope is not part of the 1921 comedy Leap Year, which has a Non-Indicative Name.
- The Pirate Movie, being based on The Pirates of Penzance, shares its source material's 21st year/birthday plot point.
- The 2006 South Korean horror film succinctly named February 29 revolves around a mysterious killing related to an urban legend of a ghostly murderer who strikes every four years on Leap Day.
- In Whit by Iain Banks, the Luskentyrian cult consider those born on the 29th of February to be sacred, so they have an orgy nine months before that date.
- In the appendix of The Lord of the Rings, the Shire celebrates an extra day named Overlithe, which occurs once every 4 years in the middle of summer (around mid-June).
- In the novel series How to Train Your Dragon, Hiccup was born on Leap Day.
- The Frasier episode "Look Before You Leap" takes place on a Leap Day. Frasier encourages everyone to "take a leap" and try something new. One of Martin's friends was also born on Leap Day.
- The Middle: Sue Heck is a Leap baby who dreamt of actually celebrating her 16th birthday on Feb 29, 2012.
- Cameron on Modern Family is also a Leap Day baby. Phil also takes Feb. 29 off to enjoy this "bonus day".
- My Hero: Piers Crispin's father told him his birthday was on February 29th, thereby ensuring he only got one present every four years.
- Jerry on Parks and Recreation was born on this day.
- 30 Rock: Leap Day William emerges from the Marianas Trench dressed in blue and yellow on February 29. There is even a movie about him starring Jim Carrey in the vein of The Santa Clause.
- On Wings, Roy was born on Feb. 29 and held a birthday party for himself every four years, saying he was 10 when he was 40 or whatever the precise dates were. While Roy acknowledged his real age, the tradition was that everyone would throw him a kids' party based on his Leap Year age.
- In The Pirates of Penzance, the Pirate King and Ruth inform Frederick that he is bound to serve them, not until his twenty-first year, but until his twenty-first birthday.
Through some singular coincidence—I shouldn't be surprised if it were owing to the agency of an ill-natured fairy—
You are the victim of this clumsy arrangement, having been born in leap-year, on the twenty-ninth of February,
And so, by a simple arithmetical process, you'll easily discover,
That though you've lived 21 years, yet, if we go by birthdays, you're only 5 and a little bit over!
- When the characters' official birthdays were revealed in Dance Central 3, Dare's birthday was on February 29.
- Teen Genius Genki Girl Precis F. Newman from Star Ocean: The Second Story has born in this day, according to the visual art-book.
- In Temple of Elemental Evil Bertram winds up enslaved until his "twenty first birthday" (i.e. 84 years) due to his being born on this date, most likely a Shout Out to The Pirates of Penzance.
- In And Shine Heaven Now, this is how Annie Warbucks explains how she looked no older than 30 (in 1998) and still could be alive during World War II: because she was born on this day, she ages at the quarter of a rate of a normal human. Of course, she could just be pulling Seras's leg. (That particular comic was posted on April Fool's Day, after all.) This is based on the canonical explanation for why Annie hasn't aged in sync with the real world, incidentally.
- Howard Tayler of Schlock Mercenary is among those born on February 29.
- Michelle from the webcomic Scrambled Eggs was born on February 29. The birthday parties this Dumb Blonde holds every four years have become Cool and Unusual Punishments for the other characters.
- In one Nedroid comic, Leap Day goes horribly wrong.
- "It was April the 41st, being a quadruple leap year..."
- In the SuperMarioLogan episode, "Cody's Birthday!", it is revealed that Cody was born on February 29. Cody makes the mistake of telling Bowser Junior and Joseph that he's eight years old, but technically due to the laws of time, actually two years old. As a prank, Junior and Joseph go as far as to make a baby-themed birthday party for him and pretend that he's a baby himself.
- Here's a list of performers born on February 29.
- As noted, Irish folklore marks February 29 as the day women are allowed to propose to men, explained as a deal Saint Bridget struck with Saint Patrick.
- As a curiosity, when Julius Caesar had the calendar reformed, the year 46 BC was made 445 days long to get up to date, making it the longest year in history.
- Canadian comedian Sugar Sammy was born on the suitably funny day of February 29.