Nov 17th at the earliest. I haven't seen this mentioned here yet, but provisional ballots in Ohio may not be counted until the 17th. That means that if the Ohio results are close enough, and if the EC is as close as everyone is saying, that there won't be a known winner in the Buckeye State until later in November, and by extension a winner in the Electoral College won't be known until later in November also. I'm going to say right now, I expect that this will end in lawyers. I don't see anyone right now with a big enough margin in the Electoral College that would stop that.