St. Patrick's Day is celebrated on March 17th to honor St. Patrick, the patron saint of Ireland, who was executed around AD 461. The holiday commemorates St. Patrick's spread of Christianity in Ireland during the 5th century. Traditions include wearing green, eating Irish foods, and drinking beer. People also dress in costumes, often dressing as leprechauns or wearing funny green hats and shirts decorated with shamrocks or rainbows.