Every year on the 17th of March, cities around the world turn green. Rivers are dyed emerald, skyscrapers glow with green lighting, bars overflow with people wearing shamrocks and hats, and supermarkets sell themed merchandise ranging from green beer to novelty clothing. What began as a religious feast day honouring Ireland’s patron saint has evolved into a global cultural and commercial phenomenon. St Patrick’s Day now illustrates how tradition, migration, and marketing can