In the comic musical “Pirates of Penzance,” the main character Frederic thinks he will be released from servitude to pirates in the 21st year of his life — but he’s actually indentured until his 21st birth date.
Frederic was born on a leap day, meaning his 21st birth date won’t happen until he’s 84 years old.
This calendrical phenomenon has translated into a variety of similar cultural traditions and references across the globe.
According to an article published by Purdue University Cooperative Extension Service, women were not allowed to propose to men in fifth-century Ireland. But according to legend, St. Bridget was frustrated by how long it took men to propose, so St. Patrick declared that women could propose to men only on Feb. 29. This was written into law in Scotland in 1288.
“Any man who declined the proposal by a woman on Feb. 29 would be fined a fee owed to the lady. The fine may be a kiss, a dress or other money,” according to the article.
Some traditions surrounding leap year are still practiced today. According to the article, Greeks consider a leap year to be bad luck, and one in five couples living in Greece will not marry during one of these years.
UNM astronomy professor Richard Rand said the leap year occurs because of a discrepancy between the amount of time it takes for the sun to rotate around the Earth and the time allotted by our Gregorian calendar.
“We always make sure that the summer solstice and the winter solstice occur at the same time every year,” he said. “The time it takes for the Earth to go around the sun is not the same as the year that we use.”
Rand said the Earth orbits the sun in 365.256 days, but our calendar runs on a 365.2422 day year.
He said the calendar year is slightly shorter because the Earth’s axis wobbles slightly and completes a rotation every 26,000 years. The slight change in position of the Earth’s axis means the summer solstice arrives 18 minutes earlier every year.
“It very, very slowly does a wobble, which is called precession,” Rand said. “About 13,000 years from now, the summer solstice will occur on the other side of the orbit.”
He said our calendar is based on a number close to 365.25 days, which is why we add a day every four years.
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“It’s just to counteract that it doesn’t take the Earth 365.0 days to travel around the sun,” he said.
