This thread is devoted to discussing the Arkham Universe as a whole which is composed of a series of Arkham related comics as well as the series of games. To kick things off I've enclosed a timeline I found online that outlines the major timeline of the series.

Year 0 - Kirigi Initiation
Year 1
Year 2
December 24th-25th
Arkham Origins Incident - set 10 years prior to Asylum in year 2, Asylum in year 12
December 31st
Cold, Cold Heart
Year 3
February
Blackgate Incident
Dick Grayson becomes Robin - shown in Multiplayer and he isn't in Arkham Origins Blackgate
Year 4
Year 5
Year 6
Barbra Gordon becomes Batgirl
Year 7
Dick Grayson leaves Gotham and becomes Nightwing
Year 8
Jason Todd becomes Robin
Year 9
Assault on Arkham
Year 10
Jason is ‘killed’ by the Joker
Tim becomes Robin - mentioned in game that he became Robin 6 months after Jason's 'death' so it likely occurred in the same year
Batgirl: a Matter of Family - Tim is a very new Robin in this likely only just starting his career
Barbra is paralyzed by the Joker - this could be placed in year 11 as well either at the end of 10 or beginning of 11
Year 11
July
Arkham Asylum Incident - roughly 10 years after Origins
Year 12
Year 13
February
Arkham City Incident - 18 months after Asylum
March
Harley Quinn’s Revenge - 2 weeks after City
October
Harley Quinn preorder DLC
October 31st