by: Michelle Barnhart
It is common knowledge that sometimes February has an extra day. Feb. 29, or leap day, comes around once every four years. 2020 will be one of those years. But why have a day that only exists 25% of the time?
Erik Johnson, astronomy professor here at Parkland, provided some background on leap years.
“Astronomy has long been one of the ways we tell time,” he said. “Before our sophisticated clocks and time zones, we measured each day by the sun moving across the sky.”
Johnson explained that factors such as how high the sun was in the sky and which stars were visible at night helped people develop a 365-day calendar. This calendar made it easier for people to plan for things like agriculture and hunting seasons. But people quickly noticed something was wrong.
“We would get a few days ahead over time, so our calendar was less accurate for crop planning,” Johnson said.
Eventually, around the time of Julius Caesar, people realized that a year was about 365.25 days long. As such, an extra day was added every four years to keep the seasons in sync with the calendar. Prior to this, according to an article from History.com written by Evan Andrews, people used a “muddled lunar model” in which an extra month was added to the calendar. It wasn’t until 46 BC that Julius Caesar and astronomer Sosigenes altered the Roman calendar. This new Julian calendar declared a year as 12 months with 365 days, with a leap year occurring every four years.
“This calendar isn’t perfect, but it’s going to work well for thousands of years” – Erik Johnson
However, Johnson explained that this solution was not foolproof. About 1500 years later, it became apparent that the Julian calendar was about 11 days off. This is because a year is more precisely 365.2422 days long. To fix this, Pope Gregory XIII instituted a calendar—known as the Gregorian calendar, which is what we currently use—in which leap day is taken away three times every 400 years.
A good way to think about it, suggested by Andrews’ article, is that leap years occur every four years, except ones that are divisible by 100 but not 400. There was no leap day in 1700, 1800, or 1900, because those numbers are not divisible by 400. There was a leap day in 2000, but there will not be one in 2100.
“This calendar isn’t perfect, but it’s going to work well for thousands of years,” Johnson said. Andrews’ article stated that discrepancies with the Gregorian calendar will need to be addressed in 10,000 years or so.
There is about a 1 in 1,461, or 0.07%, chance of being born on leap day. One notable person who is a part of this group is rapper Ja Rule, who was born on February 29, 1976 in New York.
Another Leap Day baby is YouTuber Giovanni Rivera, who was born exactly 20 years after Ja Rule on February 29, 1996. Both were born in New York.
Finally, American pop singer and actress Dinah Shore was born on February 29, 1916. According to her Famous Birthday profile, she toured with USO (United Service Organizations) and performed for American soldiers overseas. Shore passed away on February 24, 1994.
As Leap Day 2020 comes around in about a week, we can appreciate this day for preventing winter holidays from becoming summer ones. We can also appreciate that this leap day is a Saturday and not another Monday.
