Birthdays is a dating simulation game. The goal of the game is to successfully date a girl of the player's choice. The player first chooses a birthday and a name for his alter ego. Then he is presented with a calendar for the year. Visiting different locations (movies, shopping mall, etc.) leads to meetings with different girls. After learning their phone numbers, it becomes possible to call them and set a date. During dates, the player often has to choose between different dialogue lines to please the girl. It is also possible to buy present for the ladies. It is entirely possible to set dates with multiple girls, but they might meet each other and become jealous. Girls also don't take it lightly if you don't appear on a date. Finally, at the protagonist's next birthday, the most impressed girl will agree to have sex with him. The sex scenes are explicit, but rather few.