Chief Justice John Roberts administered the oath of office to Obama in the Blue Room of the White House - before live television cameras but without a public audience - shortly before noon when his first term ended officially.
But since Jan 20, the designated inauguration day in the Constitution happens to be a Sunday, he will take the oath again Monday on the steps of the Capitol with all the pomp and ceremony watched by some 800,000 Americans now converging on the capital.
Ronald Reagan was the last president to do the same, for his second inauguration in 1985. Before him Dwight D. Eisenhower did so in 1957.
Obama Sunday joined not only the fraternity of 21 second-term presidents, but the even more exclusive group of seven presidents whose inaugurations have fallen on a Sunday.
(Arun Kumar can be contacted at arun.kumar@ians.in)