Watching for Christ's Return

On May 24 of this year Family Radio evangelist Harold Camping reaffirmed his October, 2011 date for the end of the world. Camping justifies his previous miss of May 21 as the end date, dubbing that a “spiritual judgment” occurred instead. But what does the Bible say about certainty regarding the Day of the Lord? Is Jesus Christ literally and physically returning to earth to judge the nations? What is the duty of each Christian, indeed of everyone, in view of Christ’s coming?