List of presidents of the United States by time in office
| Longest presidency | Shortest presidency |
Franklin D. Roosevelt 4,422 days | William Henry Harrison 31 days |
The length of a full four-year term of office for a president of the United States usually amounts to 1,461 days. The listed number of days is calculated as the difference between dates, which counts the number of calendar days except the first day. If the first day were included, all numbers would be one day more, except Grover Cleveland would have two more days, as he served two full nonconsecutive terms.
Of the individuals elected president, four died of natural causes while in office, four were assassinated, and one resigned from office.
William Henry Harrison spent the shortest time in office, while Franklin D. Roosevelt spent the longest. Roosevelt is the only American 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 limitation.
While there have been 47 presidencies in the nation's history, only 45 people have been sworn into office; Grover Cleveland and Donald Trump were elected to two nonconsecutive terms.