A date on the calendar this week may have some doing a double-take: Feb. 29. It's known as a Leap Day during 2024, also known as a Leap Year, but why is that and how often does it happen?
Here's what you should know:
What is a leap year?
A leap year means there's an extra day in the calendar.
Why do we have leap years?
"It takes approximately 365.25 days for Earth to orbit the Sun — a solar year. We usually round the days in a calendar year to 365. To make up for the missing partial day, we add one day to our calendar approximately every four years. That is a leap year," according to NASA.
What is a leap day?
During a leap year, the month of February has an extra day added to it. So this year, there will be 29 days in February, rather than 28. That 29th day is also referred to as a "leap day."
When are leap years and why don't they happen every four years exactly?
Feeling out of the loop? We'll catch you up on the Chicago news you need to know. Sign up for the weekly Chicago Catch-Up newsletter.
Leap years happen almost every four years. That means 2024 and 2028 will both be leap years.
But still, there are some exceptions to the once-every-four-years rules. That's because "it takes Earth approximately 365.242189 days, or 365 days, 5 hours, 48 minutes, and 45 seconds, to circle once around the Sun," according to Time and Date.
"If the tropical year waspreciselysix hours longer than a calendar year with 365 days, we could use theJulian calendar, which adds aleap day every 4 years without exception. The deviation would grow to exactly 24 hours over 4 years, and Earth would need exactly one day to catch up to the position in its orbit where it was four years prior," the publication states. "However, the deviation between the common year and the tropical year is a littlelessthan six hours. The Gregorian calendar addresses this by employing aslightly more complicated set of rulesto determine which years are leap years. It's still not perfect, but the resulting deviation isvery small."
How can you calculate a leap year?
There is a set of rules for determining whether a year is a leap year. And, according to the Farmer's Almanac, those are:
- A year may be a leap year if it is evenly divisible by4.
- Years divisible by 100 (century years such as 1900 or 2000) cannot be leap yearsunless they are also divisible by 400. (For this reason, the years 1700, 1800, and 1900 were not leap years, but the years 1600 and 2000were.)
What if you are born during a leap year?
According to the Almanac, people born on a leap day during a leap year are known as "leaplings." Some cultures see the birthday as a sign of good luck.
