Leap Year typically takes place every four years. The process of adding a day to the calendar every four years was designed to realign the clock and calendar more closely with how long it takes the Earth to rotate around the sun, which is slightly longer than the 365 days attributed to a year. If not for Leap Year, the seasons would slowly shift out of place.

There are many interesting facts to learn about Leap Year, and this year, with February 29 on the calendar, is the perfect time to explore them.

It takes the Earth 365 days, 5 hours, 48 minutes and 45 seconds to circle once around the sun, says Time and Date. Without leap years, we’d lose almost six hours every year. After a century, the calendar would be off by nearly 24 days.

Despite 2100, the next turn of the century, being divisible by four, it will not be a leap year. That’s because it is divisible by 100 but not 400, which means it will not be a leap year. This exception to the rule pertains to new century years.

Forbes reports that it’s likely the calendar will need to be changed again since the Earth’s rotation rate, the axial tilt orientation and the Earth’s orbital motion around the sun is not constant. Various effects, such as earthquakes and something called tidal braking, affect the passage of time.

Legend states that on February 29 it is alright for a woman to propose to a man, a custom attributed to St. Bridget. Bridget complained to St. Patrick that some women had to wait too long for their suitors to pop the question. As the legend goes, Patrick supposedly provided women this day to propose to compensate.

Some cultures view February 29 as an unlucky day. In Greece, couples are warned against planning weddings during leap years. In Italy, the phrase, “Anno biseto, anno funesto” (“leap year, doom year”) is uttered.

Individuals who are born on February 29th are known as leaplings or leapers.

Leap Day is not considered a legal day. Those who are leaplings have to choose February 28 or March 1 for their official and legal birthdays.

Individuals who are paid fixed monthly incomes often work for free on February 29th because their wages will not be calculated to include the extra day.

Guinness World Records indicates the only family it could verify as producing three consecutive generations born on leap days belongs to the Keoghs. The elder Patrick Anthony Keogh was born in 1940, his son Peter Eric was born in 1964, and his granddaughter Bethany in 1996.