Most years, February 28 gives way to March 1. But not this year! In 2012, we have a February 29, and we’ll have another one in 2016. What’s up with that?
Our calendar year is usually 365 days. This is the amount of time that it takes Earth to travel once around the Sun. When the Gregorian calendar was introduced in 1582, a year was defined as 365 days to make the calendar year coincide with the solar year.
Long, long ago, though, smart astronomers figured out that it actually takes Earth a little bit longer than 365 days to travel around the Sun. Measuring precisely, they determined that one trip around the Sun actually takes 365.242 days (or 365 days, 5 hours, 48 minutes and 46 seconds, to be exact).
That means a year should actually be 365 and almost one-quarter days long. Since that would be very difficult to manage on a calendar, the ancient Egyptians came up with the idea of adding a day every four years to keep the calendar year on track with the solar year.
The ancient Romans under Julius Caesar decided to do the same as the Egyptians when they developed our modern calendar. In fact, they were the first to designate February 29 as the extra day.
This extra day is called Leap Day. The year in which it occurs is called a Leap Year, since it has 366 days and helps the calendar leap one day forward to stay on track with the Earth’s journey around the Sun.
Is all this really necessary? An extra day every four years may not seem like a big deal now, but it adds up over time. For example, after a century, the difference between the calendar and solar years would be 25 days. That would mean that seasons would start almost a month later than they’re supposed to. Leap years help correct this problem and keep the calendar on track.
Unfortunately, the math turned out to be just a bit more complicated than merely adding a day every four years. Astronomers figured out that the solar year is really 11 minutes and 14 seconds less than 365 and one-quarter days. That means adding a day every four years would lead to three more days than necessary being added every 400 years.
To solve this problem, the ancient Romans decided to skip leap years three times every 400 years. The rule they put in place is this: only one out of every four “century” years is considered a leap year. For example, 1700, 1800 and 1900 were not leap years, but 2000 was.
The easy way to know whether a century year is a leap year is to determine whether it’s evenly divisible by 400. So, 2100, 2200 and 2300 will not be leap years, but 2400 will be a leap year.
People born on February 29 are often called “leaplings” or “leapers.” In non-leap years — called common years — they usually celebrate their birthdays on either February 28 or March 1. Some “leapers” take advantage of their special birthday when they get older. For example, an 84-year-old “leapling” might claim he’s only 21, since he’s only celebrated 21 birthdays (every four years)!
(20 votes, avg. 4.80 out of 5) 
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My cousin just had her 6th birthday today, and I had already had mine in January. I’m going to be 10 before she has her 7th birthday. Ha!Ha!Ha!Ha!Ha!Ha!
That’s a really cool family connection to today’s Wonder, Saffron! Thanks so much for sharing it with us! Please tell your cousin that everyone in Wonderopolis wishes her a HAPPY BIRTHDAY!
LEAP YEAR!!!!!
That’s right, Hannah! Happy Leap Day to you…THANKS for visiting today’s Wonder of the Day®!
I get it.. wow, that is so cool.. okay I’ve got to go.. bye
It makes us super happy to hear that you understand a little more about Leap Year after exploring today’s Wonder of the Day®, Sydney! Thanks for being a GREAT Wonder Friend!
We have a leapling in our classroom. His name is Nolan. He is only 2 years old today. He is a VERY mature 2 year old. Thank you for helping us understand why we have a “leap” year.
First of all, HAPPY BIRTHDAY, Nolan! You are the youngest 2nd grader we know (wink, wink)! Secondly, THANK YOU to all of Mrs. Phillips’ WONDERful students for always making our day much brighter with your awesome WONDERing! Happy Leap Day to you all!
Here are some of our thoughts and questions about Leap Day:
1. Why is it that someone who is 21 years old looks really old?
2. Leap Day is weird.
3. Do you turn a year older when you don’t have Leap Day but you were born on Leap Day?
4. Leap Year is interesting. Why did the astronomers want to make Leap Year?
5. Leap Day is hard to understand.
6. Is it correct in your article to say “helps the calendar leap one day forward to stay on track with the Earth’s journey around the Sun?” OR does it go one day BACKWARD. (We’re staying in February one more day instead of going forward to March.)
Here are some predictions about tomorrow’s Wonder:
1. a giant person/cake,
2. someone eating a giraffe,
3. the tallest person on Earth,
4. the first armor for the Colosseum,
5. a smoothie (some people might order a tall smoothie).
We have to say, we LOVE all the WONDERing you guys did about Leap Day today, New Century School 2/3 Class–Verona, WI! Do you know what? Your awesome thinking and curiosity always makes US wonder more, too! That’s a GREAT thing, so THANK YOU!
Those are some WONDERful predictions about tomorrow’s Wonder, too!
So I can see myself in the future today?! That’s so cool. Ha,ha,ha. I wonder what I’ll look like in 2016? Gotta go.
It’s really cool to WONDER what we will all look like in the future, Stefani! Thanks so much for checking out today’s Wonder about Leap Year! We appreciate your comment!
Dear Wonderopolis,
We are leaping with excitement and joy to learn about leap year. Avery’s friend is a leapling. She is 2 leap years (but really she is 8). Do you know who gave leap year its name? Where could we find out how many people are born on leap year? We also heard that the ancient farmers needed to have leap year so their plantings could go as scheduled. Do you know anything about that?
Thanks!
Mrs. Johnson’s third grade
Happy Leap Day, Mrs. Johnson’s Third Grade! Thanks so much for visiting today’s Wonder and for sharing your AWESOME questions! We found an article on the national news channel ABC’s website that has a great quote from a man named Peter Brouwer (who is a leapling, himself): “The law of averages means your chance of being born on Feb. 29 are one out of 1,461…We figure in the U.S., there’s about 200,000 of us, and in the world, about 5 million.”
We think that’s a LOT of Leap Year babies, don’t you? We’ll all have to do a bit more WONDERing about your other questions!
Dear Wonderopolis,
We love your Leap Day video. One of our students has an uncle who is celebrating his birthday today–he will turn 9!!
Your information really helped to answer our questions about this special day. Thanks for showing us this video!
Sincerely,
Kids in Room 305
Hello to everyone in Mrs. Kennedy’s Class! We’re so glad you stopped by Wonderopolis today and enjoyed exploring today’s Wonder together! Thanks for letting us know you liked the video, too!
I think it’s leap year! LEAP YEAR!!!!!! HAHAHAHAHHAHAHAHAHAHAH
It IS Leap Year, Kalea! Thanks for hanging out with us in Wonderopolis on this “extra” day of 2011!
I don’t even know what leap year is but…
LEAP YEAR!!!!!
Hello, Avery! We hope you had a chance to explore this Wonder of the Day® and learn what Leap Year is and why today is so special!
After reading about the wonder of the day we have a question. How did the astronomers actually do their measuring?
That’s a WONDERful question, Mrs. Smith’s Grade 2,3 class! Thanks so much! Part of the fun of visiting Wonderopolis is doing extra WONDERing about any Wonder of the Day® you visit! We encourage you to take a learning journey together to discover how astronomers did their measuring. We hope you will share what you find out with everyone here in Wonderopolis…we’d all LOVE to learn about that, too!
My twin’s 4th grade teacher has a friend who was born in the leap year! I think Leap year is really interesting! Do you have any wonders about computers, ipods, headphones or any electronic supplies? HAPPY LEAP DAY, WONDEROPOLIS!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
P.S I think tomorrow’s wonder is either about Paul Bunyan or tall people.
That’s a really neat connection to this Wonder, Missy! We’re sure glad you shared it (and your guess for tomorrow’s Wonder) with us today! We have some past Wonders we think you might enjoy:
Wonder #420 – How Do Touch Screens Work? http://wonderopolis.org/wonder/how-do-touch-screens-work/
Wonder #346 – Is a Computer Bug an Insect? http://wonderopolis.org/wonder/is-a-computer-bug-an-insect/
Wonder #206 – What Is a Mouse? http://wonderopolis.org/wonder/what-is-a-mouse/
Wonder #269 – Why Do They Call It a “Tall Tale”? http://wonderopolis.org/wonder/why-do-they-call-it-a-tall-tale/
Happy WONDERing!
Happy birthday to everyone who is celebrating their birthday today!
That’s a super nice thing to say, Amoolya! We hope everyone who was born on Leap Day has a GREAT birthday today, too!
Wonderpolis that was awesome!!!!!!!!!!!!!!!!!
thank you.
We’re so glad you thought today’s Wonder was awesome, Kyle! That makes us super happy to hear!
That’s awesome.
Thanks for letting us know what you thought about today’s Wonder, Ellis! Happy Leap Day!
Why did the video have vegitales in it???????
Hi, Maddie! Thanks for your great question! We search high and low for the best videos to go with each day’s Wonder. We chose the video for today’s Wonder because we thought it helped explain Leap Year in a fun, colorful way!
I LOVE LEAP YEAR!!!!!!!!!!!!! I LOVE THE VIDEO. THANK YOU FOR THE COOL VIDEOS. IT ONLY COMES 1 TIME IN FOUR YEARS. I AM GOING TO SPEND MY LEAP YEAR WITH MY FRIENDS. HAPPY LEAP YEAR!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
Happy Leap Year to you, too, Kaitlyn! Thanks for your enthusiastic comment…we can tell you really love Leap Year! We think spending the day with your friends sounds like a perfect way to celebrate February 29th!
I will be 14 on the next Leap Day!
That is WONDERful, Kevin! Happy birthday AND happy Leap Day!
Mrs. Wilwert’s 1st graders find the idea of Leap Year very confusing but think Larry the Cucumber is very funny!
Thanks for letting us know what you guys thought of the video for today’s Wonder, Mr. P. and Mrs. Wilwert’s 1st graders! We thought Larry and his friends made learning about Leap Year fun, too!
So cool to learn about leap year!!!!!! YAY!!! LEAP YEAR!!!!
We appreciate your enthusiastic comment today, Trecy! Thanks for being excited to learn about Leap Year!
We enjoyed discussing the wonder today. We are still confused about when it says we skip Leap year 3 times every 400 years. How do we know which years out of the century (every 400yrs) are skipped. Can you give us another explanation? Thanks!
Thanks so much for visiting this Wonder of the Day®, Miss Higgins’ Class, and THANK YOU for the extra WONDERing you all did about Leap Year! We think your question is GREAT! We’ll have to do a bit more WONDERing about that ourselves! You can find some more information and really AWESOME links and activities in this “Today is Leap Day” resource from ReadWriteThink.org: http://www.readwritethink.org/classroom-resources/calendar-activities/today-leap-20443.html.
That video was funny and cool. I liked how you guys added 6+6+6+6 = 24 thing. I never thought of it that way. Happy leap year!
Thanks for telling us that you liked the video for today’s Wonder, Hannah! Happy Leap Year to you, too!
That was a great wonder!
Hello, Emsiepiedoe! We’re glad you thought today’s Wonder was GREAT! We appreciate your comment!
Hi. It’s me again. So, I loved the video and the article too. So, I thank I know why you did this wonder today…because it is leap year day today. That is why you did that today, right? Tell me if I’m right, ok?
You are always on the time with these new wonders of the day thing. I think you guys are always busy like all the time, right? My bro said hi and my family says hi to y’all wonder workers and wishes you good luck on this day.
I’ve got a ? for you… is one of you born on leap year?
We really liked reading your comment today, Ashlyn! YES! Today’s Wonder is about Leap Year because today is Leap Day…YOU WERE RIGHT! Please tell your brother and the rest of your family that everyone in Wonderopolis thinks they ROCK! We think YOU rock, too, Ashlyn!
Dear Wonderopolis,
Great wonder for today! There is an extra day every 4 years because the earth tilts and extra 360 degrees every 4 years so we need an extra day. My teacher gave us a trick question today. It was if Sally’s birthday is today and she is 7, how old is she. She is 28 since she was born a leap year. I think tomorrow’s wonder is about bugs. XOXOXOXOXO,
Paige
WOW! You sure know a LOT about Leap Year, Paige! Thanks for sharing all the cool things you know with your friends in Wonderopolis today…happy Leap Day!
I am happy to learn about Leap Year with the video!
Woo, hoo! We’re happy that YOU’RE happy, Albert! Thank you for being such a GREAT Wonder Friend!
I was glad to learn that in 2016 we will have another leap year. Also, that people born on leap day are called leaplings or leapers.
Thanks for sharing some cool facts you learned about Leap Year today, Adel! We’re so glad you stopped by Wonderopolis today!
I love the video!! Great job today!
Thanks for such a nice comment, Spencer…we’re glad you enjoyed the video! We sure appreciate you stopping by Wonderopolis today!
Thank you so much for posting this wonder. I have WONDERful days on ones where I check the wonder. Learned so much!!
We’re glad Wonderopolis is a part of your day, Carrie510! Thank you for letting us know! We hope you learned a little more about Leap Year by exploring this Wonder and we hope you had a WONDERful Leap Day, too!
I have a huge question, answer truthfully. Do you like your job answering us kids? And what is the weirdest question you have ever gotten?
Those are SUPER questions, Devan! YES, yes, yes! We really DO like communicating with our Wonder Friends through the comments you leave for us! It’s SO MUCH FUN to hear what you guys like about a Wonder, what you learn from visiting Wonderopolis and especially when you share personal connections to each Wonder of the Day®! We get LOTS of comments each day, and try our best to reply to each authentic one! We have had some really funny ones, really smart ones, and really off-topic ones, but you know what? They are ALL AMAZING because they came from AWESOME Wonder Friends just like YOU!
I have like an super awesome plead of excitement. You should do a wonder of the day on how the first steps to getting famous. If you look at all the pop stars and actors, there was always a beginning point. I want to be famous, but how can I get recognized besides singing at a old folks home like I do every weekend?
That sounds like a great idea for a future Wonder of the Day®, Zachary! We think it’s AWESOME that you sing in your community every weekend…way to go! We’re sure you bring LOTS of joy to the residents of the facility you sing for!
BES ROCKS on Wonderful Wednesday-so excited to see more classes joining the WONDER comment section. I have to admit Miss. Higgin’s class asked me the same question and I didn’t know the answer. Our class chose the mathematical solution (every 4 years 1/4=1) which makes LEAP year. Great thinking at BES!!!
We agree, Mrs. Caplin! What WONDERful Wonder Friends we have in BES students and teachers!
I have always wondered…if you are born on February 29th, every year that is not a leap year, do you still get older? Say I am 21, but I was born on Feb 29th would I really be 84 years old?
Hello, Team Wilch 5! Yes, people who are born on Leap Day grow and age just like everyone else. People think it’s funny to say a “leapling” who is really 40 is still 10 years old. It’s just another fun way to learn about Leap Year!
Thank you wonderopolis. Now I know what leap year is and I know some people who’s b-days are on leap year.
You’re welcome, Avery! We want to thank YOU for visiting this Wonder of the Day® and leaving us such a GREAT comment!