What is a leap year?

About this episode

What is a leap year? 2008, 2012, 2016, 2020... a leap year comes along every four years, lasting 366 days instead of 365 as you probably know. In a leap year, the shortest month of the year, February, has 29 days instead of 28. So if you’re born on February 29th, you only get to celebrate on that exact date when a leap year occurs. Every other year, you’ll need to decide on which date to celebrate: February 28th or March 1st. Most people opt for the latter out of superstition. People born on February 29th are sometimes known as ‘leaplings’, ‘leapers’ or ‘leap year babies’. Some famous leaplings include rapper Ja Rule, actress Caitlin E.J. Meyer and motivational speaker Tony Robbins. Leaplings should beware the leap year bug, which affects computer systems that are programmed with the rule that a year always has 365 days. Similar issues can affect administrative paperwork. So where did the weird idea of adding an extra calendar day every four years come from? We actually measure time based on planet Earth’s rotations on its own axis and orbits around the sun. The planet takes one day to fully rotate around itself, like a spinning top! It takes a lot longer to complete one full orbit of the sun however, adding up to one year or slightly over 365 days. This is known as a tropical or solar year. That’s right, the duration is over 365 days because a tropical year is never made up of an exact number of days. When the Earth gets back to its starting position after a full orbit, it has rotated 365 times on its own axis, plus an additional quarter-rotation which makes all the difference. If you want to be really precise, you should know that the exact length of a tropical year can vary by up to 30 minutes. We could simply delay the start of every year by a quarter of a day to compensate for the difference. But that would end up affecting the time of day, as well as our system of seasons in a year. So we stick to 365 days, and add an extra day every leap year to best synchronize with our calendar. So how far back was this system created and who decided on it? In under 3 minutes, we answer your questions! To listen the last episodes, you can click here: What is nudge theory? What is a showrunner? What is the anti-mask movement? See acast.com/privacy for privacy and opt-out information. Learn more about your ad choices. Visit megaphone.fm/adchoices