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Professor Astro Cat Explains Why Leap Year Is Cooler Than Your Kid Thinks

Like Daylight Savings Time, Groundhog Day, or drinking green beer, leap year is one of those things that parents have a hard time explaining to their kids when it appears on the calendar. You can say one of 3 things when the question comes up. 1) “Because” (a surprisingly popular option). 2) “Go ask Siri.” Or 3) “Go ask Professor Astro Cat.”

Dr. Dominic Walliman is the author of the popular series of kids’ books that explain how space works. While the world thinks that February 29 is just a messed up day to fix our broken calendar, it is actually a great way to introduce all kinds of astronomical concepts, from Earth’s orbit to the relative nature of space and time. Best to put on some Pink Floyd while explaining.

The Axis Power
If you haven’t already started teaching your kid about the stars, now is a perfect time to start. Wait for a clear night, and take a little hike away from your cul-de-sac’s light pollution. Find the North Star (aka Polaris) — it’s usually the brightest thing in the sky that’s twinkling (if it’s not twinkling, you’re looking at a planet or a police helicopter.)


That star represents the direction the Earth’s axis is pointing. Now produce an orange and an apple from your pocket (should have mentioned that earlier). Stick a pencil through the orange (also, you need a pencil). Tell your little Copernicus that, like the Earth’s axis, the eraser always points in the same direction. So, as the orange Earth goes around the apple Sun, the top and bottom alternate closer and farther away depending on where it is in orbit.

“The measure of a real “space year” would be however long it takes for the axis to get from 1 point — where it’s exactly facing the sun — all the way around to the same point again,” says Dr. Walliman. Unfortunately, our calendar doesn’t go by something as cool as space years.

There Aren’t 365 Days In a Year
After you children get the concept of the Earth, the Sun, and why you were carrying around a bunch of fruit, it’s time to blow some minds.



Start by saying it takes about 365 and a quarter days to go around the sun — emphasis on the word about. Because really it takes 365.2421897 days (that’s 365 days, 5 hours, 48 minutes, 46 seconds) to get from axis point to the same axis point. In order to make up that fractional amount of time, we just wait 4 years to add an extra day, or leap day.

Without that leap day, he explains, “Summer would slowly creep into autumn, autumn would creep into winter. Before long, the middle of winter would be warm and sunny.” And how would that be a bad thing?


Out With Julian, In With Gregorian
The 12 months of the year alternate between 28, 30, and 31 days because Pope Gregory XIII, who thought that Caesar’s Julian calendar sucked, came up with his own Gregorian calendar in 1582. It’s the calendar that we still use today, and the reason why February 29 even exists. Because when you’re the Pope, you can pull those kinds of power moves (provided you have really good astronomers).

Flickr / Bryan Kennedy

Sometimes We Miss A Leap Year
One more mind-blowing fact. You may have noticed that .2421897 doesn’t actually total up to 6 hours per year. If we didn’t account for the remaining fraction, every 150 years we’d be a whole day out. To correct that, you skip a leap year when it’s a year that can be divided by 100. If that year is also divisible by 400 — like in 2000 — you don’t. So, the next chance for your kid to be really confused is the year 2100, when humanity has hopefully solved this clusterf–k of space-time.

Are Kids Born On February 29 In Birthday Limbo?
Yes and no. Unlike the rest of us normals who were born on a day and time you can set your watch to, leap day babies are in temporal purgatory. But there is a way out. Take the time your baby was born, match it against the location of the axis at that time (you can calculate that here — warning, it may make the non-scientist’s brain melt), and then you can work on what day that falls on each year. Depending on when they’re born, they’ll celebrate on either February 28 or March 1. Or you can just lie to them and pick a nice, warm day in June.