Ready for a leap year, Idaho? Here’s what that means and why we started observing them
If you were hoping for an extra day before your rent is due or just a bonus day to prepare for March Madness, you’re in luck. That’s because every four years, an extra day comes at the end of February, making the month 29 days long instead of its typical 28 days.
It’s called a leap year. But why do we add on an extra day every four years, and why do we call it a leap year?
Here’s what to know.
What is a leap year?
As mentioned above, a leap year is when we add one more day to the end of February.
We do this because the Earth’s rotation around the sun isn’t exactly 365 days. It actually takes 365.25 days — or 365 days and 6 hours — to orbit around the sun, according to NASA.
Because of the additional 6 hours each year, without adding an extra day, the hours would slowly accumulate. In turn, this would gradually shift our seasons over time at a rate of six hours per year.
According to the Smithsonian Institute, within 700 years, summers in the Northern Hemisphere would start in December, and winters would begin in June. The shifting seasons wouldn’t necessarily be devastating — humans lived for thousands of years before the invention of the leap year in 45 BCE — but it would cause a slow shift in the monthly timing of many things, such as crop farming and rainy or dry seasons.
Adding an extra day in February every four years helps keep our calendar on track with Earth’s solar orbit, meaning our months stay tied to the typical seasons we associate them with.
Interestingly, a full day also isn’t 24 hours — it’s 23.26 hours, according to the Smithsonian Institute. That means that each time we add a leap year, we make the calendar 44 minutes longer every four years.
To combat that problem, we skip leap years on years that are divisible by 100 and not divisible by 400. That means we had a leap year in 2000, but we skipped leap years in 1800 and 1900 and will skip it again in 2100.
Doing so ensures that our calendar doesn’t slowly drift because of our leap year adjustment.
When were leap years created, and by whom?
Humans have been observing leap years for almost 2,000 years. The idea came from Roman emperor Julius Caesar.
The Romans originally had a 355-day calendar, according to Britannica, so that they could keep their significant festivals around the same season every year. They’d add an extra 22- or 23-day month every two years to align the months and seasons.
But in 45 BCE, Caesar decided to simplify things by adding days to the calendar, creating the 365-day calendar structure we know today. In doing so, he also created leap years to offset the drifting seasons.
What does it mean for us in Idaho?
While the addition of leap years almost 2,000 years ago was an ingenious idea, its year-to-year impact isn’t all that significant.
You’ll get an extra day to pay any start-of-month bills or rent, and those with a birthday on Feb. 29 will actually get to celebrate on their birth date rather than on March 1. And no — someone born on Feb. 29 doesn’t only age up every four years; the law does not care for the quirks of the calendar.
The biggest change for many if leap years weren’t invented is that we’d currently technically be in early July 2025. That doesn’t mean it would be summer outside — we’d just be experiencing the current February-like temperatures in the middle of summer, and our Christmases would be spent in the sun rather than bundled up indoors.
