On 20 January, Barack Obama is officially sworn in as US president at a ceremony in the nation's capital, Washington DC, becoming the first African-American to lead the nation.
The swearing-in takes place on the West Front of the US Capitol
It is also the day President George W Bush leaves the White House after two terms in office.
Huge crowds are expected in Washington to witness the ceremony at the Capitol and the parade. For the first time, the entire length of the National Mall will be open for those who do not have tickets for the ceremony. Big screens will relay the day's events to them.
Later in the day a series of inaugural balls, official and unofficial, takes place in locations around the city. Mr Obama is expected to attend 10 balls in the course of the evening.
Keep this guide to the inauguration to hand to check what will be happening when and what to look out for.
INAUGURATION ON THE BBC
1600-2100 GMT: Live video on BBC News website, available to UK and overseas users
1600-1800 GMT: Live coverage of inaugural ceremony on BBC One and BBC News channel, simulcast on BBC World News and BBC America
1600-1900 GMT: Radio 5 Live Drive comes from Washington
1630-1800 GMT: Extended programme on BBC Radio 4's PM
1900-2100 GMT: Parade to the White House on BBC News channel, simulcast on BBC World News and BBC America
2230-2340 GMT: Extended programme on BBC Two Newsnight
0000-0100 GMT (Weds): Inauguration special on BBC World News America
0300-0400 GMT (Weds): Inauguration special on BBC World News America
0900 GMT (0400 EST): The National Mall opens for people without tickets for the swearing-in ceremony to start entering the area. They will be able to watch on giant screens.
1000 GMT (0500 EST): Washington's Metro system starts running; services are likely to be busy with as many as 2m people expected to congregate in the city centre.
1300 GMT (0800 EST): People with tickets to watch the swearing-in ceremony at the US Capitol can start entering the area.
1455 GMT (0955 EST): President George W Bush and First Lady Laura welcome President-elect Barack Obama and Michelle to the White House for coffee.
1500 GMT (1000 EST): The inaugural festivities start. They will include music from the US Marine Band, San Francisco Boys Chorus and San Francisco Girls Chorus.
Some people will watch the ceremony from the inaugural platform
1630 GMT (1130 EST): Mr Obama and Vice-President-elect Joe Biden arrive at the Capitol for the official inaugural ceremony on the West Front Lawn. Mr and Mrs Bush participate at the event.
Mr Biden is sworn in as vice-president.
1700 GMT (1200 EST): Barack Obama takes the oath of office, administered by using President Abraham Lincoln's inaugural Bible. He then delivers the inaugural address, his first speech as President of the United States. It is expected to last just under 20 minutes.
1740 GMT (1240 EST): President Obama escorts former President George W Bush and former Vice-President Dick Cheney as they leave for a departure ceremony.
1805 GMT (1305 EST): Mr Obama attends an inaugural lunch in the Capitol's Statuary Hall.
1825 GMT (1325 EST): Mr Bush speaks at Andrews Air Force Base in Maryland, before boarding a flight for Texas.
Barack Obama will watch the parade from a special viewing stand
1920 GMT (1420 EST): Mr Obama begins a review of the troops. The 56th Inaugural Parade then makes its way from the Capitol via Pennsylvania Avenue to the White House. Mr Obama watches from a bullet-proof viewing stand between Lafayette Park and the White House.
Crowds line the parade route to see the procession pass by - made up of marching bands, military cadets, high school bands, dance troupes, civic organisations and performers, all picked by the Presidential Inaugural Committee.
0020 GMT (1920 EST): Mr and Mrs Obama leave the White House for the first of 10 official inaugural balls they will attend in the course of the evening. Singer Beyonce will perform the first dance song. They include the Neighbourhood Ball, the Obama Home States (Illinois and Hawaii) Ball, the Biden Home States (Pennsylvania and Delaware) Ball and the Youth Ball.
A number of unofficial balls also take place, hosted by various organisations and companies.
0725 GMT (0225 EST): The Obamas leave their last ball to return to the White House, their new home.
Timings subject to change.