Clause 4: Election Day"The Congress may determine the Time of chusing [sic] the Electors, and the Day on which they shall give their Votes; which Day shall be the same throughout the United States.
Congress sets a national Election Day. Currently, Electors are chosen on the Tuesday following the first Monday in November, in the year before the President's term is to expire. The Electors cast their votes on the Monday following the second Wednesday in December of that year. Thereafter, the votes are opened and counted by the Vice President, as President of the Senate, in a joint session of Congress.
Our Founding Fathers specifically set forth "a national Election Day" -- not days. In the early days of national elections it was no easy logistical task to vote. People had to plan to cast their ballot. Many citizens had to endure long travel and hardship to cast their ballot on a single day.
...In 1792, Congress passed a law establishing November as the month for presidential elections to be conducted. This gave enough time for elections to be conducted, for voting and tabulating to take place before the next legislative session. In 1845, Congress set forth that "the first Tuesday after the first Monday in November" became the official day of presidential elections. Now you may ask yourself, why Tuesday? The answer is that many people had to travel great distances to cast their vote so Mondays was planned for as a day of travel. Sunday was never even considered because of its religious significance.