There is a specific date in law, sometime in mid-December, when the electoral college will meet and cast their votes.
This means that prior to that date, that each individual state needs to have certified their election returns.
It would be pretty neat for Trump to pull a page out of the Obama playbook and decide how (or if) a law is going to be applied...
Rubio introduced a bill to do the direct opposite of what you propose. I believe he wants to delay it until after New Years.