St. Patrick’s Day has been celebrated since the 17th century. It was originally Feast Day in Christianity to remember the death of St. Patrick who used the three-leaf clover to describe the trinity.
Today we observe this day by wearing green. If you don’t wear green, anyone who notices is allowed to pinch you. Look out Ist-fems, your safe space may be invaded.
Also, many people use today as an excuse to consume vast amounts of beer.