Timeline

Unknown time ago(Between 2000 and 200 years ago)

 * Yamamoto founds the Shinigami Academy
 * Formation of the Gotei 13
 * Jūshirō Ukitake, Shunsui Kyōraku are among the first students to graduate from the Academy.
 * Captains Yamamoto, Retsu Unohana, Jūshirō Ukitake, Shunsui Kyōraku and other unknown shinigami make up the "old guard"

Aprox. 108 years ago

 * Captain of 3rd division retires - Rōjūrō Otoribashi promoted to 3rd division captain.
 * Captain Hikifune of the 12th division has been promoted to the Royal Guard. Kisuke Urahara, 3rd seat of the 2nd division is promoted as 12th Division captain.

Current day - Substitute Shinigami/Soul Society Arc

 * Ichigo Kurosaki, unknowing son of a powerful shinigami, takes shinigami powers from Rukia Kuchiki