Sanvers Big Bang 2021 ran from June 13 to December 24, with June 13 to October 31 being the writing and art period and November 1 to December 24 being the posting period.
Requirements
Sign up before June 13
writers: write a new, or finish an as of yet unposted, story with at least 20k words
artists: create art of any kind (drawing, video, moodboard etc.) for the story you got assigned to
beta readers: support the writer, proofreading etc.Initial info thread: https://twitter.com/bigbangsanvers/status/1393297460492124160
Detailed timeline
June 12: Sign-up form closed
June 27: Form for writers to send in their story idea closed (including potential trigger warnings) and option to request a beta reader
July 4: Forms for artists and beta readers to choose their top 5 stories closed (included an option to select fanfics they didn't want to be matched with)
July 7: Matches got sent out
July 14: First check-in with participants
July 18: Deadline for writers to send their matches a general outline of their story (roughly 5k words or 4 scenes)
October 17: initial deadline for all works
October 31: extended deadline after consultation of participants
November 1: first story and art revealed
December 24: last story and art revealed
You want to (re-)read all the amazing stories and look at the accompanying artwork? Check out the ao3 collection!