Casual Pi Day, also known as Pi Approximation Day, is celebrated every July 22 in the United States. This day honors the mathematical constant Pi, using the fraction 22/7 as its approximate value. To celebrate, individuals often bake pies and share their love for mathematics with friends and family. Many bakeries and restaurants participate by offering pie specials, including discounts from chains like Marie Callender's and Baker's Square. Local pizzerias, such as Domino's and Pizza Hut, may also feature deals on 'pizza pies.' Social media engagement is encouraged, with people sharing photos of their pies and fun math facts related to Pi using hashtags like #CasualPiDay. Overall, the day combines a celebration of mathematics with culinary enjoyment.