Glaring Error In Final Episode

Well, my "Sorkin Fest" has come to an end, I spent basically the last two months (re)watching all four* of his TV shows, all of which rank pretty high in my list of favorites...Kind of a shame to have such an obvious misstep in the cold open of the last episode of TWW, to wit:

Railing against how cold it will be outside on the dais during the inauguration, Abbey Bartlett asks "Who in his right mind decided that January would be the right time to hold an outdoor ceremony north of the equator?" President Bartlett replies "Jefferson, Adams, Franklin". President Bartlett, being a fan of historical minutiae, would know better. Inauguration Day, was on March 4 from 1793 until 1933. It was changed to January 20th by the 20th amendment.