In what month do you vote for president?
The public "votes for President" in November, but they are actually electing members to the electoral college in that election. The electoral college casts the votes for President (and Vice President) in December.
The 538 electors are chosen based on each state's popular vote on the day after the first Monday of November. Those electors then cast their votes for U. S. president and vice president on the Monday after the second Wednesday of December. November. It occurs on the first Tuesday after the first Monday (I.e. can't be the first day of the month).