Did we ever confirm what D5 means? December 5?
Hard deadlines:
December 8: Deadline for states to resolve election disputes themselves
December 14: Electoral College votes
January 6: Congress certifies the Electoral College results
January 20: Inauguration
That would work. I think Jan 6 is the true deadline to affect change. SCOTUS might still have authority to invalidate electors from a state after they have voted, but after Congress certifies on Jan 6, there is no Constitutional provision for what happens after that. Then it gets really messy.