It only happens once every 4 years (and sometimes, once every 8 years!) In honor of Leap Year 2020, here are 29 Facts About Leap Day.

1. A Leap Year happens every 4 years.

2. The Earth takes 365 days, 5 hours, 48 minutes, and 46 seconds to travel around the sun, just a smidgen longer than a calendar year.

3. The ancient Egyptians first realized the solar year and the man-made calendar were not always in sync.

4. It doesn’t seem like cause for a whole extra day, but those hours added up over the centuries, so an extra day was added to the calendar.

5. People once used a 355-day calendar with an extra 22-day month every two years, but in 45BC Julius Caesar ordered his astronomer, Sosigenes, to simplify things.

6. The Romans were the first to call February 29 Leap Day.

7. Under Julius Caesar, all months had 30 or 31 days. Caesar’s month, July, had 31. August had only 29 days. When Caesar Augustus became Emperor, he added two days to ‘his’ month to make August the same as July. He took those days from February.

8. The current formula of a Leap Year every 4 years was officially adopted in the 16th century.

9. In years divisible by 100, there is no Leap Year (unless the year is divisible by 400). That means 1900 was not a Leap Year, but 2000 was a Leap Year.

10. The longest we can go between 2 leap years is 8 years. This last occurred between 1896 and 1904. The next time it happens will be between 2096 and 2104.

11. Since the Earth makes a complete revolution around the sun in 365 days, 5 hours, 48 minutes, and 46 seconds, adding a day every four years doesn’t “add up” mathematically.

12. The marginal difference of 0.000125 days between the Gregorian calendar average year and the actual year means that, in 8,000 years, the calendar will be about one day behind where it is now.

13. People born on February 29 only have 1 “real” birthday every 4 years.

14. People born on February 29 are called Leapers or Leaplings.

15. Some places like China and New Zealand, recognize Feb 28 as a Leaper’s legal birthday.

16. The United States recognizes March 1 as the legal birthday for Leapers (if it isn’t Leap Year).

17. Because different governments recognize different dates for Leapers, if you timed it right, flying from one country to the other, you could enjoy the world’s longest birthday.

18. People born on Feb. 29 usually blow out their candles on Feb. 28 or March 1 instead.

19. According to History.com, about 4.1 million people around the world have been born on Feb. 29, and the chances of having a Leap birthday are one in 1,461.

20. Many people feel that to be born on Leap Day is a sign of good luck.

21. Superstitious Chinese believe children born in a February during Leap Year are harder to raise.

22. Norway’s Karin Henriksen holds the world record for giving birth to the most children on consecutive Leap Days. Daughter Heidi was born Feb. 29, 1960, son Olav in 1964, and son Lief-Martin in 1968.

23. The Keogh family of Ireland and the UK saw one generation born on February 29, 1940, his son born on the same date in 1964, and a granddaughter arrive on February 29 in 1996.

24. Anthony, Texas calls itself “Leap Year Capital of the World.” Whenever Feb. 29 rolls around, they hold a festival.

25. US Presidential Elections and the Summer Olympics occur during Leap Years.

26. Famous people born on Leap Day include composer Gioacchino Rossini (1792), poet Lord Byron, motivational speaker Tony Robbins, jazz musician Jimmy Dorsey, and soccer player Darren Ambrose.

27. There’s even a Leap Year club. The Honor Society of Leap Year Day Babies is a club for people born on Feb. 29. More than 11,000 people worldwide are members.

28. A famous fictional occurrence of a Leaper is in Gilbert and Sullivan’s 1879 comic opera The Pirates of Penzance: as a child, Frederic was apprenticed to a band of pirates until his 21st birthday. Having passed his 21st year, he leaves the pirate band. However, his indenture papers commit him to remain a pirate until his “21st birthday,” not his “21st year” so he must return to the pirates until he is 84 years old.