“...the date has been set by Federal law since 1845.”
The date of the presidential election was set by the Constitution in 1781.
Check your History.
There is no Constitution of the United States before 1787, and no ratification in force until June, 1788.
Now double-check your Constitution, because there is no requirement in the Constitution except that electors must be chosen before the safe haven date. In fact, there is not even a requirement that the states choose their electors by a popular vote.
An excerpt from a long article to refresh your memory:
No federal law regulated the 1788 federal election. In 1792, federal law permitted each state to conduct presidential elections in the state (i.e., to choose their electors) at any time in a 34-day period before the first Wednesday of December, which was the day set for the meeting of the electors of the U.S. president and vice-president (the Electoral College), in their respective states.
More detail at many places, among them Wikipedia: https://en.wikipedia.org/wiki/Election_Day_(United_States)#cite_note-2