For we Christians the "end of the world" coincides with Jesus' return. The New Testament speaks of certain events that we can expect to see prior to Jesus' second advent. As interesting as a N.T. "End Times" Scavenger Hunt would be, I realize that you are pressed for time, so I'll point you toward the great summary in the Catechism (click here for paragraphs 673-677, complete with Scriptural citations in the footnotes), and list two things we should expect to see:
1) a large number of Jewish people will recognize Jesus as the Messiah, and
2) a tremendous, final persecution of the Church will break out at the instigation of the antichrist.
We have had a number of Jewish converts over the past several decades, but I don't think it qualifies as the recognition by "all Israel." And although the Church is persecuted around the world, I don't see how the present state of affairs could be identified as the antichrist's final assault upon the Church. Things may be bad, but I envision the Church's final passion as something much more grueling. Even if we had witnessed these two events, Jesus still assures us that the exact "day and hour no one knows, not even the angels of heaven" (Mt. 24:36).
None of this is to say that we shouldn't live December 21st as if it was our last day. As individuals, it might very well be. The Lord may come tomorrow to take your or me to Himself through death; He may come before this day ends. How should a Christian spend his or her last day? I don't think it has to be anything over the top; our usual daily tasks are sufficient in the Lord's eyes. "Whatever you do, whether in word or deed, do it all in the name of the Lord Jesus, giving thanks to God the Father through him" (Col. 3:17). We should simply focus upon what the Lord has called us to be - sons or daughters, sisters or brothers, husbands or wives, parents, neighbors, workers - and with His grace, live those vocations to the best of our ability. As Jesus said, "It will be good for that servant whose Master finds him doing so when he returns" (Mt. 24:46).