In 999, people feared the Four Horsemen of the Apocalypse: war, social collapse, famine and death.

Our generation gets a Fifth Horseman: Y2K.

We live in an age steeped in apocalyptic messages, religious and secular, real and imagined: Hiroshima. Branch Davidians. Holes in the ozone layer. "Blade Runner." Littleton, Colo. Heaven's Gate. The Unabomber.

Into the midst of this "Apocalypse Now" culture wanders Y2K, the year 2000 computer problem. It's an irresistible symbol for its age: a time bomb of technology and human folly with a millennial trigger date. Our world of 6 billion people has built its foundation upon the ability of computers to do simple, first-grade arithmetic with dates--except we've screwed up the dates.

So it's now 1999, and our response to the crisis looks surprisingly medieval--a revival of spirituality and apocalyptic thinking, a yearning for a world-shattering event that will shake humanity out of its self-destructive ways and bring about, at long last, an era of sanity, reverence and peace, however one defines those.

The year 999 gave way to 1000 without much fanfare, according to the predominant view among today's medieval historians. A Burgundian monk, Rodulfus Glaber, left a rare account reporting widespread panic and omens ranging from earthquakes to weeping statues of the Virgin Mary.

In 999, time was a fluid concept measured by heavenly bodies, water flow and folklore. In 1999, time is a concept sliced into 10 billionths of a second by atomic clocks and into five-minute modules by hand-held electronic organizers.

In 999, Armageddon was a biblical battle so vast and inconceivable it could be waged only by the forces of Jesus and Satan. In 1999, Armageddon--in the form of nuclear holocaust, environmental destruction, biological warfare, televised genocide and economic collapse--is a tangible, everyday worry that seems to rank somewhere below getting the children to soccer practice on time.

In 999, global communication was nonexistent. The invention of the printing press was still more than 400 years in the future. In 1999, any 5-year-old with a free library Internet connection--or Gary North, a once-obscure apocalyptic Christian who now boasts one of the world's most-trafficked Y2K Web sites (www.garynorth.com)--can communicate instantly with millions.

The apocalyptic tradition was established long ago in the United States, beginning with Christopher Columbus. After landing in the Americas, Columbus declared "his destiny as an explorer was to fulfill God's divine plan in preparation for the millennial kingdom on Earth," Daniel Wojcik, a University of Oregon folklorist, writes in "The End of the World as We Know It: Faith, Fatalism, and Apocalypse in America."

Over the ensuing 500 years, millennial fever took on a distinctly American cast with the establishment of the Church of Jesus Christ of Latter-day Saints and Jehovah's Witnesses, both with millennial-oriented theologies.

As technology flowered in 19th-century America, so did spiritual preparation for the millennial reign of Christ forecast in Revelation, the final book of the New Testament. Revelation foresaw Earthly catastrophes, the defeat of the Antichrist, the triumphal 1,000-year reign of Christ on Earth, and the final judgment and resurrection of the dead. To prepare their bodies physically for the millennium, 19th-century Christians experimented with food: Evangelist Sylvester Graham invented the graham cracker, and Seventh-day Adventist John Harvey Kellogg perfected the corn flake.

The latest millennial flowering has occurred since World War II and the atomic bomb, when humans' annihilation first became a technological possibility. The year 2000 computer problem fits perfectly into this tradition because, like nuclear weapons and environmental devastation, it is a very real problem with very real consequences.

"We're on the edge of change," says George La Du, a Christian fundamentalist pastor who regards the year 2000 as God's wake-up call to churches. "I feel we are in a time in the church that is unprecedented. God is using Y2K as a tool to bring us together."

Unity among the people of God, says La Du, a former Catholic altar boy who once dabbled in transcendental meditation, is a sign that humans are in "the end of the end times." La Du, who leads the 25-household Jubilee Christian Fellowship in Tigard, Ore., is using Y2K as an opportunity to urge people to prepare "clean hearts," love their neighbors and let the glory of God flow through them.

Michael Dowd, who works as an organizer of ecologically sustainable communities, also believes Y2K is a wake-up call. But he sees it in secular terms--an opportunity for Western society to rethink the way its people live their lives and run their institutions.

"Y2K will bring up some of the oversights, the shortcomings, the shadow side, the abuses, the down side of our modern, technological, industrial world," says Dowd, who founded the Portland, Ore., Metro Y2K Citizens Task Force after pondering the potential devastation of systemic, worldwide computer failures.

Like La Du, Dowd sees a divine hand--and a message of hope--in the scope, timing and nature of Y2K.

"What if this wasn't a cosmic mistake?" says Dowd, a former Christian pastor. "What if somehow there was purpose or design or at least a hidden blessing or a possibility present here that otherwise might not be?"

Not everyone, of course, is a Y2K "believer." But Y2K "atheists," such as Nicholas Zvegintzov, a widely quoted computer programmer, are outmanned and outgunned in public forums by larger numbers of Y2K activists. Zvegintzov calls Y2K a technological problem surrounded by "hype, exaggeration, alarmism, ignorance and deliberately misleading promotion."

Dowd says all views--believers and atheists alike--are legitimate and must be acknowledged.

Where does this leave the many Y2K "agnostics," who wonder who and what they should believe?

"In the Y2K problem," writes Richard Landes, director of the Center for Millennial Studies at Boston University, "I can get experts who claim nothing significant will happen (owls), and others who claim that it will be a catastrophe (roosters). Neither can be certain, even if they insist they are, even if they will prove right.

"Our dilemma is, who to believe? The future is 'fact free' because it hasn't happened yet, and we don't know what will happen."