Answer:
This is a list of presidents of the United States by time in office. The basis of the list is the difference between dates. The length of a full four-year presidential term of office amounts to 1,461 days (three common years of 365 days plus one leap year of 366 days). If counted by number of calendar days all the figures would be one greater, with the exception of Grover Cleveland, who would receive two days.
Since 1789, there have been 44 people sworn into office as President of the United States, and 45 presidencies, as Grover Cleveland served two non-consecutive terms and is counted chronologically as both the 22nd and 24th president. Of the individuals elected president, four (William Henry Harrison,[1] Zachary Taylor,[2] Warren G. Harding,[3] and Franklin D. Roosevelt) died of natural causes while in office, four (Abraham Lincoln,[4] James A. Garfield,[4][5] William McKinley,[6] and John F. Kennedy) were assassinated, and one (Richard Nixon[7]) resigned from office.
William Henry Harrison spent the shortest time in office while Franklin D. Roosevelt spent the longest. Roosevelt is the only US president to have served more than two terms. Following ratification of the Twenty-second Amendment in 1951, presidents—beginning with Dwight D. Eisenhower—have been ineligible for election to a third term or, after serving more than two years of a term to which some other person was elected president, to a second term. The amendment contained a grandfather clause that explicitly exempted the incumbent president, then Harry S. Truman, from the new term limitations, which first applied to his immediate successor, Dwight D. Eisenhower.
