The Electoral College: A2020 Presidential Election Timeline
December 8, 2020: The "Safe Harbor" Deadline - This is the date states should have any challenges resolved, and their vote counts certified by their respective secretaries of state.
December 14, 2020: Electors Vote in Their States
December 23, 2020: Certificates Must Be Delivered to the Designated Officials
January 6, 2021: Joint Session of Congress to Count Electoral Votes and Declare Election Results Meets
Expect any legal challenges to be fast tracked to keep their results within the December 8th safe harbor date.
Adding, in theory, if a state’s vote cannot be certified by December 14th, in theory, that states’s slate of electors cannot be designated, and cannot meet, and therefore that state cannot cast its electoral votes.
That could lead to neither candidate having a majority, forcing the election to the congress.