Former first daughter Chelsea Clinton headlined a National Day of Service gathering under a tent on the National Mall, where she said she had been inspired by her grandmother, as well as her famous parents. She urged her audience to become part of a ‘‘chain of service’’ by helping the less fortunate.

Biden and his wife, Jill, spent time at an armory pitching in as volunteers packed 100,000 care kits for deployed members of the military, wounded warriors, veterans and first responders.

Biden credited former President George H. W. Bush, a Republican, for starting the ‘‘Points of Light’’ program, which was a sponsor of the event. He said service was an antidote to ‘‘the coarsening of our culture. We've got to get back to reaching out to people.’’

In the evening, Mrs. Obama and Mrs. Biden hosted the Kids’ Inaugural Concert, an event paying special tribute to military spouses and children.

Families invited to the event cheered Usher as he sang his hit ‘‘Yeah!’’ Katy Perry, who donned star and stripes for her song ‘‘Firework,’’ told the audience, ‘‘I'm very proud to be here ... and to see the Obamas and the Bidens here for four more years.’’

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