On Saturday, March 3, 1849, at noon, President James Polk’s presidential term ended. The new president, Zachary Taylor, was to be sworn in the following day, but Taylor refused, as it was a Sunday. Vice President-elect Millard Fillmore also refused to be sworn in on that day, on the same grounds. The swearing-in ceremony was therefore postponed to Monday, March 5, which meant that, by presidential succession law, David Atchison, the President pro tempore was President for one day: March 4. In an interview, Atchison admitted to sleeping through most of his presidency, as he had had four busy nights finishing up work at the Senate.
Despite the fact that he is not on the official list of presidents, David Atchison does have a presidential library/museum in his honor. The Atchison County Historical Museum in Atchison, Kansas—a town that was named for him—is, appropriately, the smallest presidential library in the United States.