President Barack Obama takes the oath of office Sunday surrounded by family in an intimate inauguration ceremony at the White House. Watch live streaming video here at 11:55AM.

A gift shop displays presidential memorabilia (Mario Tama/Getty Images)

The subdued swearing-in is a function of the calendar and the Constitution, which says presidents automatically begin their new terms at noon on Jan. 20. Because that date fell this year on a Sunday — a day on which inaugural ceremonies historically are not held — organizers scheduled a second, public swearing-in for Monday.

A crowd of up to 800,000 people is expected to gather on the National Mall to witness the second inauguration.

Vice President Joe Biden will also be sworn in Sunday in a small, early morning ceremony at the Naval Observatory, his official residence.

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