Realized not everyone has seen these.
These are from Chu’s GDC 2017 talk that he gave ealier this year. In it, certain events are roughly outlined. Note that Reflections was the last comic released.
1. 30 years ago from in-game present time: the Omnic Crisis occurs. Duration of the event is not given.
2. The Omnic Crisis ends and the Golden Age of Overwatch begins. This duration lasts approximately 20 years according to the Soldier: 76 origin video.
3. During the Golden Age of Overwatch, “The Last Bastion” occurs.
4. Approximately 5 years ago from the in-game present time, the “Fall of Overwatch” begins. Duration is not given.
5. However at least four major events occur: Halloween (“Junkenstein’s Revenge” comic), Null Sector’s Uprising (not pictured), Doomfist’s arrest (not pictured), and Ana’s battle with Widowmaker (Ana’s first comic “Legacy”).
6. Shortly before the in-game time, “Recall” occurs.
7. “Alive,” “Dragons,” and “Hero” occur “around the same time” as Recall.
7.5. Winston’s “Are you with us?” Recall message is sent out.
8. Six comics occur in approximately the same time frame as Recall and the other shorts - McCree, Junkers, Torbjörn, Symmetra, Reinhardt, and Pharah.
9. Sometime after Pharah’s Mission Statement and after Recall, the Old Soldiers comic occurs.
10. Holiday season “post the game’s release” (so November - December after Recall) is when Reflection occurs.
11. Hypothetically, after Reflections comes “Infiltration” and the Bastion comic.
12. Approximately February after Reflections, “Masquerade” occurs (Carnival in Venice gives us a timeframe).
13. Sometime after Masquerade, Doomfist attacks Numbani and destroys the OR-15s. Efi Oladele rebuilds one into Orisa.
14. Post-Orisa PTR updates: the Numbani map has been fixed up (mostly). Lucio’s concert on Numbani is either over or not being advetised anymore.
Number 14 is now approximately the current “in-game time,” although the game itself is not canon. The game’s “official release” is marked in the canon timeline to show both: 1) the environmental story-telling that occurred in the game at the time of the release and 2) to show any changes to environmental story-telling since release. This includes things such as: Necropolis/Castillo/Black Forest being developed, Horizon Lunar Colony being included, and the new Chateau Guillard map. I personally tend to see each map (or changes to maps such as on Numbani) as a “snapshot” into a canon moment in the timeline rather than as an explicit timeline event. The exception to this is Uprising.
Hope this helps!