What is a leap year? Here's the science behind the extra day.
Why do we have leap years? The reason for this extra day on February 29th is more complicated than you think.
2024 is a leap year, meaning Thursday, February 29, is a quadrennial event.
Since leap years typically occur every four years (although there are some exceptions), our last leap days were 2020 and 2016, and the next leap year will occur in 2028.
And since this day doesn't happen often, people celebrate in different ways: companies offer special offers to commemorate it, others finally celebrate their birthday on February 29th.
Here's everything you need to know about Leap Day, including what it is, why it occurs every four years, and when it was created.
Leap day offers 2024: Get discounts and free food at Wendy's, Chipotle, Krispy Kreme and more
What is a leap day?
A leap day is an additional day added to the calendar. During a leap year, which occurs every four years, leap day falls on February 29, giving the shortest month of the year an extra day.
Why is there a leap day every four years?
The reason there are leap days and years is because of the Earth's orbit.
The number of days it takes the Earth to complete one revolution around the Sun is not a whole number. According to the National Air and Space Museum, the 365 days we experience are actually 365.242190 days.
Getting rid of those 0.242190 days adds up.
This fraction allows the seasons to be arranged correctly each year. If leap day were omitted from the calendar, the months in which we normally experience each season would eventually shift. This would impact other aspects of life, such as growing and harvesting crops.
Added together, four 0.242190 days equals approximately one full day, which is why February 29 is added to the calendar of most years divisible by four, including 2024.
When do we skip Leap Day?
To compensate for decimals, we sometimes skip leap years, but this is rare. Prepare for a bit of math: Years divisible by 100 but not 400 are skipped, meaning we skipped leap years in 1700, 1800, and 1900, but not in 2000. Next Leap year, which we will skip, is quite far away, in the year 2100.
How often is there a leap year? Here's the next leap day after 2024 and when we'll (eventually) skip one
Who created Leap Day?
The concept of adding leap days is not new and has been around for thousands of years, Britannica reports. Some calendars – such as the Hebrew, Chinese and Buddhist calendars – included intercalary months, also known as “intermediate months,” according to the History Channel.
While Julius Caesar is often credited with inventing leap days, the idea originated with the Egyptians. In the third century B.C. In the 4th century BC, the Egyptians followed a solar calendar that was 365 days long and included a leap year every four years, reports National Geographic.
In ancient Rome, their calendar varied and included a 23-day intercalary month called “Mercedonius.” But it wasn't a standalone month. According to the History Channel, Mercedonius was added to February to make up for the difference between the Roman year and the solar year.
When creating the Julian calendar, Caesar took inspiration from the Egyptians and decided to add an extra day to the month of February every four years. The Julian calendar officially began on January 1, 45 BC. BC
This method would continue for several centuries, but not without problems. Caesar's calculation of 365.25 days was obvious, but it was not the exact 365.242190 days that the solar year contains. To be precise, “Caesar overestimated the solar year by 11 minutes,” reports the History Channel. According to National Geographic, this meant the Julian calendar would be one day shorter every 128 years.
In the 16th century, time had shifted again, and not in a positive way. Important dates had changed, including Easter. The holiday is said to occur on the first Sunday after the first full moon on or after the vernal equinox. At this point, the date of Easter had shifted by about ten days.
To remedy this, Pope Gregory XIII introduced introduced the Gregorian calendar, which, according to the History Channel, included a leap day every four years but eliminated it in century years that were not divisible by 400. For this reason, 1700, 1800 and 1900 were not leap years, but 2000 was.
Despite its accuracy, the Gregorian calendar is not without errors. Instead of deviating by one day every 128 years, like the Julian calendar, the Gregorian calendar deviates once every 3,030 years, the History Channel reports.
Upcoming leap days
This year, 2024, is a leap year. Leap Day falls on Thursday, February 29th.
The next leap years will be 2028, 2032 and 2036.
Leap Day Deals: Where to score on groceries, produce and more on February 29th
Grocery chains like Wendy's, Chipotle and Krispy Kreme are offering specials and free food in honor of Leap Day. Here you can score points with discounts.
What happens if you are born on a leap day?
February 29th is the rarest birthday someone can have. According to the History Channel, at least 5 million people still celebrate their birthdays on a leap day. Your chance of being born on February 29th is one in 1,461.
Many “leaplings” (or those born on a leap day) celebrate their birthday on February 28th or March 1st during a typical 365-day year, even if the documents show it to be February 29th.
25 has never looked so good: An Oklahoma woman born on Leap Day is celebrating her 100th birthday
Meet Mary Lea Forsythe: She turns 100 on Leap Day, but it's only her 25th birthday.
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