Bilbo and Frodo Baggins share a birthday on 22 September.
In Tolkien’s legendarium, Bilbo and Frodo were both born on 22 September. Bilbo’s birthday is especially important in The Fellowship of the Ring because his eleventy-first birthday party occurs on that date. Frodo also reaches an important age on the same day, turning 33 when Bilbo turns 111.
The shared date links the two Hobbits and helps explain why Bilbo’s birthday celebration is also a major narrative opening. At the party, Bilbo announces his departure from the Shire and uses the One Ring to disappear, leaving Frodo to inherit Bag End and the Ring.
The date is sometimes confused with the date of the party itself in film adaptations or with Tolkien-related commemorations. In the story, 22 September is the birthday date; the party’s exact presentation can vary by adaptation and calendar context.