When Bilbo was ninety-nine he adopted Frodo as his heir, and brought him to live at Bag End; and the hopes of the Sackville-Bagginses were finally dashed. Bilbo and Frodo happened to have the same birthday, September 22nd. ‘You had better come and live here, Frodo my lad,’ said Bilbo one day; ‘and then we can celebrate our birthday-parties together.’ At that time Frodo was still in his tweens, as the hobbits called the irresponsible twenties between childhood and the coming of age at thirty-three.

Twelve more years passed. Each year the Bagginses had given very lively combined birthday-parties at Bag End; but now it was understood that something quite exceptional was being planned for that autumn. Bilbo was going to be eleventy-one, 111, a rather curious number, and a very respectable age for a hobbit (the Old Took himself had only reached 130); and Frodo was going to be thirty-three, 33, an important number: the date of his ‘coming of age’.