Bilbo and Frodo Baggins share the celebrated birthday of 22 September in Tolkien’s stories.
Bilbo was born on 22 September 2890 of the Third Age, while Frodo was born on 22 September 2968. The date is therefore a shared birthday separated by 78 years. Bilbo’s 111th birthday party, described at the beginning of The Fellowship of the Ring, takes place on 22 September 3001 and also marks Frodo’s 33rd birthday.
This date has become known in the real world as Hobbit Day, part of the annual celebration called Tolkien Week. Some calendars and fan communities use the occasion for readings, costumes, meals, and other activities inspired by the Shire.
The date is sometimes confused with the date Frodo leaves Bag End. In the book, Frodo begins his journey from Hobbiton on 23 September 3018, the day after his fiftieth birthday. Thus 22 September is the birthday, while 23 September is the departure date for the quest.