Formally embarking on his second term, President Barack Obama will take the oath of office Sunday surrounded by family in an intimate inauguration at the White House, 24 hours before re-enacting the ceremony before an excited crowd of hundreds of thousands outdoors at the Capitol.

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 that event, which will take place on the Capitol's red, white and blue bunting-draped west front. Supreme Court Chief Justice John Roberts, who famously flubbed the oath of office that Obama took in 2009, will swear the president in both days.

Vice President Joe Biden will also be sworn in Sunday in a small, early morning ceremony at the Naval Observatory, his official residence. Justice Sonia Sotomayor, who was appointed by Obama during his first term, will administer the oath of office to the vice president.

Once the celebrations are over, Obama will plunge into a second-term agenda still dominated by the economy, which slowly churned out of recession during his first four years in office. The president will also seek to cement his legacy with sweeping domestic changes, pledging to achieve both an immigration overhaul and stricter gun laws despite opposition from a divided Congress.

But for one weekend at least, Washington was putting politics aside. Obama called the nation's inaugural traditions "a symbol of how our democracy works and how we peacefully transfer power."

"But it should also be an affirmation that we're all in this together," he said Saturday, as he opened a weekend of inaugural activities at a Washington elementary school.

Only a small group of family members is expected to attend Obama's Sunday swearing-in, including first lady Michelle Obama and daughters Malia and Sasha. A small group of reporters will also be in the room to witness the event.

Roberts will administer the oath of office shortly before noon in the White House Blue Room, an oval space with majestic views of the South Lawn and the Washington Monument. Named for the color of the drapes, upholstery and carpet, the Blue Room is not typically used for ceremonies and instead has primarily been a reception room as well as the site of the only presidential wedding held in the White House, between then-President Grover Cleveland and Frances Folsum in 1886.

Later Sunday, Obama and Biden will speak at an inaugural reception attended by supporters.

But the president will save his most expansive remarks for Monday, when he delivers his second inaugural address to the crowd gathered on the Mall and millions more watching across the country and the world. Obama started working on the speech in early December and was still tinkering with it into the weekend, aides said.

The president's address will set the stage for the policy objectives he seeks to achieve in his second term, including speeding up the economic recovery, passing comprehensive immigration and gun control measures and ending the war in Afghanistan. However, aides said Obama would save the specifics of those agenda items for his Feb. 12 State of the Union address.

The president launched a weekend of inaugural activities Saturday by heading up a National Day of Service. Along with his family, Obama helped hundreds of volunteers spruce up a Washington area elementary school.

His shirt sleeves rolled up, Obama donned a pair of rubber gloves, picked up a paint brush and helped volunteers stain a bookshelf.

Obama added the service event to the inaugural schedule in 2009 and is hoping it becomes a tradition followed for future presidents.

Mrs. Obama, speaking to volunteers Sunday, espoused the importance of giving back in the midst of the weekend of pomp, circumstance and celebration.

"The reason why we're here, why we're standing here, why we're able to celebrate this weekend is because a lot of people worked hard and supported us, and we've got a job to do and this is a symbol of the kind of work that we need to be doing the next four years," Michelle Obama said at Burrville Elementary.

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