The inauguration of the President of the United States is a ceremony to mark the commencement of a new four-year term of a president of the United States. An inauguration ceremony takes place for each term of a president, even if the president continues in office for a second term. Since 1937, Inauguration Day takes place on January 20 following a presidential election. The term of a president commences at noon (ET) on that day, when the Chief Justice administers the oath to the president. However, when January 20 falls on a Sunday, the Chief Justice administers the oath to the president on that day privately and then again in a public ceremony the next day, on Monday, January 21. The most recent public presidential inauguration ceremony was the swearing in of President Barack Obama to begin his second four-year term in office, which took place on Monday, January 21, 2013.
The only inauguration element mandated by the United States Constitution is that the president make an oath or affirmation before that person can "enter on the Execution" of the office of the presidency. However, over the years, various traditions have arisen that have expanded the inauguration from a simple oath-taking ceremony to a day-long event, including parades, speeches, and balls.
From the presidency of Andrew Jackson through that of Jimmy Carter, the primary Inauguration Day ceremony took place on the Capitol's East Portico. Since the 1981 inauguration of Ronald Reagan, the ceremony has been held at the Capitol's West Front. The inaugurations of William Howard Taft in 1909 and Reagan in 1985 were moved inside the Capitol because of cold, wintry weather. The inaugurations of 1817 and 1945 were held at other locations in Washington, D.C. (for very different reasons) due to the War of 1812 and World War II respectively.
When George Washington was inaugurated as the nation's first president in 1789, the oath of office was administered by Robert Livingston, Chancellor of New York State. Four years later, the oath was administered by Supreme Court Associate Justice William Cushing. Since the 1797 inauguration of John Adams it has become customary for the new president to be sworn into office by the Supreme Court's Chief Justice. There have been exceptions to this practice however. William Cranch, chief judge of the U.S. Circuit Court, administered the oath of office to John Tyler in 1841 when he succeeded to the presidency upon William Henry Harrison's death, and to Millard Fillmore in 1851 when Zachary Taylor died. In 1923, upon being informed of Warren Harding's death, while visiting his family home in Plymouth Notch, Vermont, Calvin Coolidge was sworn in as president by his father, John Calvin Coolidge, Sr., a notary public. Most recently, Federal Judge Sarah T. Hughes administered the oath of office to Lyndon B. Johnson aboard Air Force One after John F. Kennedy's assassination on November 22, 1963. When a new president assumes office intra-term due to the incumbent's death or resignation, the inauguration is kept low key, and conducted without pomp or fanfare.