Today’s Wonder of the Day was inspired by Hailey. Hailey Wonders, “How many people can have the same birthday?” Thanks for WONDERing with us, Hailey!

Happy birthday to us! Happy birthday to us! Happy birthday, Wonderopolis! Happy birthday to us!

We say it's our birthday! Is it your birthday, too? Wouldn't it be cool if you shared a birthday with Wonderopolis?

If today isn't your birthday, then you probably still share a birthday with several famous people. After all, there are now and have been a lot of famous people in the world, and there are only so many birthdays to go around.

Everyone here in Wonderopolis is excited about our birthday. We're planning on having a party with cake and ice cream. We'll probably sing a song, play some fun games, and maybe even open a few presents.

Have you ever WONDERed exactly why we do those things, though? What's the big deal with birthdays? So we were born on this day a certain number of years ago. When did birthday celebrations begin anyway?

Most scholars point to the Bible as the earliest known reference to a birthday celebration. In the Book of Genesis, the Bible mentions Pharaoh's birthday. Rather than the day Pharaoh was born, however, the celebration was probably held to remember the day Pharaoh was coronated, since that's the date on which ancient Egyptians would've believed Pharaoh made the miraculous transformation from a mortal man into a god.

Birthdays were likely only observed by religious royalty for many years. It wasn't until the time of the ancient Romans that birthdays were celebrated for the common man. Even then, these celebrations were limited to men. Women's birthdays weren't celebrated until approximately the 12th century.

Our modern birthday celebrations with a party and cake didn't come around until the late 18th century in Germany. Germans would celebrate kinderfeste, which was the precursor to the modern birthday party with a cake and candles.

In fact, Germany is usually considered the birthplace of the modern birthday cake. Early on, birthday cakes were usually only available to the wealthy, who could afford the ingredients. After the Industrial Revolution, however, ingredients were cheaper and more widely-available. In addition, many bakeries began to offer pre-made cakes at affordable prices.

If you're curious about when we started singing "Happy Birthday to You," that didn't happen until the 1920s. The song got its start as "Good Morning to All," a song written in 1893 by two Kentucky teachers, Patty and Mildred Hill, for children to sing in the mornings.

In 1924, Robert Coleman published a songbook in which he included "Good Morning to All" but changed the lyrics to what we now know as "Happy Birthday to You." It's now considered the most recognizable song in the English language.

So what's the most common birthday in the United States? Experts believe that it's October 5. We thought that was pretty neat, since Wonderopolis' birthday is October 4!

Wonder What's Next?

Tomorrow’s Wonder of the Day will take you about 100 miles off the coast of Florida!