DOn't forget about March 4th.
12th Amendment Article 2 as I recall?
And if the House of Representatives shall not choose a President whenever the right of choice shall devolve upon them, before the fourth day of March next following, then the Vice-President shall act as President, as in the case of the death or other constitutional disability of the President.[a]
https://en.wikipedia.org/wiki/Twelfth_Amendment_to_the_United_States_Constitution#Text