@Megatron found this Tumblr thread for Hogwarts Mystery that has a rough idea of the timeline for the chapters up to Year 6, including Side Quests and the Time-Limited Side Quests
And the HP wiki has some more info on the TLSQs, if it helps
The plot details of achievements in Harry Potter: Hogwarts Mystery. Most achievements occur as 3-day (72-hour) limited-time events, consisting 4-part Side Quests. Year 3's "Birds Of A Feather" and Year 5's "Ordinary Wizarding Levels" both have an additional 19-hour for its event.[1] Year 4's...
harrypotter.fandom.com