Isn’t it kind of strange that one of the most important days of your life — the day you were born — is nothing but a blur to you? You don’t remember any of it! Of course, that’s to be expected, since you were so new to the world and didn’t even know how to talk, walk or read yet!
Ever since that day, you’ve probably celebrated the anniversary of that day once each year. What are we talking about? Your birthday! You know, that day when you get cake, ice cream and all those presents?
Would you believe that some people actually celebrate TWICE each year? Not only do they celebrate the anniversary of the day they were born, they also celebrate six months later on their half birthday!
What brought about such craziness? Is it a desire for more presents? An excuse to have another party? Or are there some valid reasons to celebrate half birthdays?
Before we get to the reasons, let’s take a look at how half birthdays are calculated. Yes, some math is involved, so put on your thinking caps.
There are a couple of ways to calculate half birthdays. The first — and easiest — is simply to keep the same number of the birth date and add six months to it. For example, if your birthday is January 13, then your half birthday would be on July 13.
Of course, this easy method doesn’t always work, because not all months have the same number of days. For example, an August 30 birthday would become February 30 — a day that doesn’t exist!
If you want to be really precise, you need to add half the number of days in a year to your birth date. In a normal year, this means adding 182.5 days. In a leap year, you would add 183 days. If this sounds too complicated, don’t worry. There are plenty of websites that will do the work for you!
So what about those good reasons for celebrating half birthdays? For starters, consider kids. As they grow, six months can mean huge milestones. It can be a special time to celebrate with them as they grow up, because they grow up all too fast!
Half birthday celebrations can also be great for those people whose regular birthday might be overshadowed by a nearby holiday, such as Christmas. Likewise, kids whose birthdays fall in the summer might enjoy celebrating their half birthday, so that they can share their joy with their friends at school.
Half birthdays aren’t the only special “birthdays” that some people celebrate, though. Adopted children sometimes celebrate both their actual birthday (the day they were actually born) and the day they were adopted. Do you have any other special “birthdays” that you and your family celebrate?


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Dear Wonderopolis,
I never guessed it would be your half b-day as a topic. I think tomorrow’s wonder will be about ice-skating, rollerblading or rollerskating.
The clues about today’s Wonder were tricky, Alexis, and we’re so glad you’re here with us today!
We Wonder if you have ever celebrated your own half birthday… we bet it would be a blast! Thanks for sharing your awesome guesses for tomorrow!
Dear Wonderopolis,
I loved that video. Lucas with that monkey they make a prefect match. I thought it would be a pair of shoes or pants. Thanks for reading!
This was such a cute video the little boy with his sock monkey put the whole video together those parents must love him. You got me stumped yesterday nice work!
I think tomorrow’s wonder is about the weather!!!
I never knew that some people celebrated their HALF birthdays! I just thought it was a special TYPE of day I thought it shouldn’t be celebrated TOO much.
We think tomorrow’s wonder is going to be about soap, butter, or people slipping.
Dear wonderopolis, this is my first time at wonderopolis. Today’s wonder is so boring who wants to see a baby grow up to 6 moths why not like 10 years!? Mrs. Wall and her class yay I’m writing on wonderopolis. My aunt passed away that’s why I’m not there.
I think tomorrow’s wonder will be something to do with water.
Hey there Jacob C! We’re keeping you and your family in our thoughts, but thanks for WONDERing with us! We appreciate your comment!
The background changed
I also celebrate my ‘everything’ birthdays. A bit ago, I was ’50 everything’: 50 years + 50 months + 50 weeks + 50 days + 50 hours + 50 minutes.
What a SUPER idea, Dave6d6ky! We think you came up with a very creative way to celebrate… everything!
Your video was so funny! Lucas’ facial expressions made us crack up! It was sweet how Lucas was holding the monkey’s hand. I like how adopted kids celebrate their adoption day and their b-day! Daniel likes the idea of celebrating his real b-day and half birthday because…DOUBLE the PRESENTS!
Thanks for WONDERing with us, Mrs. Albani’s Class! We’re so excited that our Wonder Friends have been using their imaginations about half birthdays! WOHOO! Also, we think Daniel’s idea is pretty clever– talk about lots of presents! Phew!
This is a very interesting article.
Wow that’s interesting.
We’re glad you enjoyed the half birthday Wonder, Lara!
Can you do a topic about what happens when your dog gets worms or how your dog or pet gets worms??? Please
You’re in luck, Wonder Friend Serena! Take a look at this Wonder from the past:
Wonder #707– What is a Parasite? http://wonderopolis.org/wonder/what-is-a-parasite/
That’s cool that your half birthday is six months after your birthday.
It makes sense, doesn’t it Emmy? We Wonder if you have celebrated your half birthday?
Have you read wonder please do it is so good.
Please write back
Thanks so very much for recommending the book, Wonder, Kade! Some of our Wonder Friends have already read it– and LOVED it! The book, Wonder, reminds us to treat others with kindness and respect… just like this Wonder: Wonder #841 What is the Golden Rule? http://wonderopolis.org/wonder/what-is-the-golden-rule/
Dear wonderopolis,
If my birthday is March 25 then my half b-day is September 25 cool.
You’re correct, Kade– your half birthday is September 25! We Wonder what you like to do to celebrate your birthday?
I love this.
We’re glad to hear it, Lila! We hope you will celebrate your half birthday from now on!
This is so cool.
We’re so glad to hear it, Mitchell! We Wonder when your half birthday is?!