A lot has happened within the story over those nine years. Several characters have been here since the beginning, as well; but even while major events might have happened to characters, players might not recall everything.
This is an out-of-character accounting, and it does not account for everything; but it can serve as a starting place for recalling or discovering more. Further, because it outlines major events by Season - and the dates thereof - it can help lend timeline context to characters' Known History in their profiles for each Season a character was present.
Each Season has its own thread, and new Seasons will be added after their finale as a 'recap'.