Welcome to May 21st on the National Day Calendar.

Everyone knows that a great party starts with two things: great food and great friends. If you know where to pick up a perfect pizza, then you’re halfway there to one of the best ways to celebrate.

And if your friends are impressed by trivia, here’s a few pizza facts to throw into the mix.

Some give the credit for the very first pizza to the ancient Greeks with their flatbread covered in oil and spices. Others think pizza has got to have cheese, which the Romans added along with honey and bay leaves. But almost everyone agrees that the cheese of choice is mozzarella.

Today, more than two billion pounds of pizza cheese are produced every year in the United States alone!

On National Pizza Party Day, do your part by ordering extra, and watch your guests celebrate even more.

Today we also celebrate National American Red Cross Founder’s Day, Waitstaff Day, Strawberries and Cream Day, Memo Day, Endangered Species Day, Defense Transportation Day, Bike to Work Day, and NASCAR Day.