All across the world, March 14 is celebrated as National Pi Day — in honor of the mathematical constant, and not the dessert that is pie. It turns out that there are two separate days to celebrate the two completely different things, and it's easy to confuse the two occasions.

Pi Day might give you flashbacks of middle school math classes. For starters, it's a day of celebration of the mathematical constant, π (pi), or 3.14159265359, which is an approximate value.

The date on which it is celebrated includes the first three major numbers and is written as 3/14. Though the day might sound boring, some people made it fun by celebrating the number with some pizza.

March 14 is celebrated as the National Pi Day, and it's not the same as Pie Day.Creative Commons

Interestingly, Pi Day involves more of pies than math. Major food chains, including both pie and pizza joints, roll out great deals and give out discounted pies and pizzas at $3.14.

On the other hand, Pie Day is celebrated on January 23 to enjoy pies, obviously. And you can thank American nuclear engineer Charlie Papazian for creating the food holiday in the 1970s after he reportedly declared his birthday to be National Pie Day.

Really, he just proclaimed the date as a national celebration of pie. The American Pie Council, of which Jason Biggs is not a member, has sponsored the holiday since 1986.

The council states on their website: "January 23 is National Pie Day, a time to celebrate the day with pie."

The website adds: "We are encouraging pie lovers everywhere to host pie parties across the country. Whether it be with your friends, family, or co-workers, share some pie on January 23."