St. Patrick's Day is celebrated on March 17th. It originated as a Christian holiday but has also become a celebration of Irish culture. Traditions include wearing green, eating Irish foods like bacon and cabbage, drinking beer, and attending parades. The shamrock symbolizes the Christian holy trinity and was used by St. Patrick to explain it to the Irish. St. Patrick established Christianity in Ireland in the 5th century and is credited with banishing snakes from the island.