Donald Trump's presidential inauguration is scheduled to begin at noon ET. According to the U.S. Constitution's 20th Amendment, each presidential inauguration should take place Jan. 20, unless that date falls on a Sunday. Then, the president takes the oath of office in private Jan. 20, and the public event is moved to Jan. 21.

Inauguration Day occurs on Jan. 20 every four years. This year, it falls on Monday, Martin Luther King Jr. Day. The holiday was officially designated in 1983, and only one other inauguration for Bill Clinton occurred on that day.