Happy Hobbit Day!
Hobbit Day is the birthday of the hobbits Bilbo and Frodo Baggins, two fictional characters in J. R. R. Tolkien's popular set of books The Hobbit and The Lord of the Rings.
Bilbo and Frodo were said to be born on Sept. 22, but of different years. Bilbo was born in the year of 2890 and Frodo in the year of 2968 in the Third Age (1290 and 1368 respectively in Shire-Reckoning.)
Tolkien Week is the week containing Hobbit Day.
The American Tolkien Society first proclaimed Hobbit Day and Tolkien Week in 1978, and defines them as this: "Tolkien Week is observed as the calendar week containing Sept. 22, which is always observed as Hobbit Day," but acknowledges that Hobbit Day pre-dates their designation.
Due to the discrepancies between the Shire Calendar and the Gregorian Calendar there is some debate about when to celebrate Hobbit Day, since the actual birthday would be September 12 on our calendar, or possibly Sept. 14, as explained in the appendices of The Lord of the Rings.