Many do, however many do not. Bible-believing Christians do believe that someday the world as we know it will end; but God will replace this world with a new world made especially for them.
Without any rational basis, many non-Christians also believe the world will end in the foreseeable future. The sun will, of course, eventually burn out, but thousands of generations will pass before that becomes a concern.
With the year 2000 of the common era looming, we are witnessing a worldwide rise in religious fanaticism. Religious fundamentalists of all stripes are committing heinous acts in the name of God, as if the time is short and they must act immediately.
It is important to understand that all calendars are made up by the culture in control at a particular time and place. The first year of a calendar almost always begins as commemoration of some religious event. For almost 2,000 years much of the world has used the Gregorian calendar, based upon the supposed birth date of Jesus. However, scholars know that the current date of 1996 is off by at least four years.
Other cultures have their own calendars. Rosh Hashana commemorates the Jewish new year. The Chinese, too, have their own new year. Obviously, Christian fundamentalists follow the Gregorian calendar, and base their prophecies on it.
Fundamentalist Christian eschatology (an oxymoron meaning the study of future events — an oxymoron because how can one study future events?) is somewhat complicated. It consists of several elements: the second coming of Jesus; the short-lived reign of a worldwide dictator called the Antichrist; a thousand year reign of Jesus on Earth; finally, eternity with Jesus for the born again. Somewhere in between, Christians will be "raptured" into the sky with Jesus. Other Christians believe they will be left on the earth to duke it out with the anti-Christ. Depending upon who's interpretation of the Bible one believes, any of these events may happen in different sequences.
It is safe to say that most Christian fundamentalists believe we are indeed living in the last days, and that Jesus will return soon. There is much division within conservative Christianity (most liberal Christians dismiss these teachings) about the ultimate scenario. However, the approach of the year 2000 is capturing the imagination of millions of Christians and non-Christians alike.
One important way in which all this affects politics is that some Christians (particularly Christian Reconstructionists) believe that the church of Jesus Christ must take dominion of the world before Christ returns. Much of the present-day activity of the Radical Religious Right is based upon varying degrees of belief in this doctrine.