The 20th Amendment also lays out a backup if a president-elect dies or hasn't been chosen by Jan. 20. So far, that procedure has never been used.

For many years, Inauguration Day was held on March 4. However, the 20th Amendment to the Constitution, ratified in 1933, moved the date to January 20 to reduce the "lame-duck" period between ...

However, the 20th Amendment to the Constitution, ratified in 1933, moved the date to January 20 to reduce the "lame-duck" period between presidents.