At 78 and the oldest president, Biden sees a world changed

In this 1987 file photo, Sen. Joe Biden, D-Del., right, walks with his wife Jill after announcing his candidacy for president in Wilmington, Del. (AP Photo/George Widman, File)

WASHINGTON — When Joe Biden took the oath of office as the 46th president, he became not only the oldest newly inaugurated U.S. chief executive in history but also the oldest sitting president ever.