Birthday is an event in Terraria. It happens every 80 Terrarian days once you've created a new character. On that day every NPC that you have will offer you any one item that they sell for free, provided that it is not worth more than 2 Platinum Coins. Also, if a Travelling Merchant spawns on that day, any of his items that he is selling will be free, regardless of price.
- A new NPC called the Birthday Guy will spawn somewhere near your original spawn point. He will give you a 3-5 Gifts on that day. To know when he has a gift for you, talk to him and he will say, "Happy Birthday!!! Here's your gift!" He will also sell Party Balloons, Confetti, and Cake .
- A calendar will appear when you press C and it will tell you the date and also the time, so you don't need to craft a Watch.
- A message will appear, "Happy birthday, <character name>!".