An American Christian organization spreading the gospel of a May 21 judgment day is the latest in a line of doomsday groups older than Noah himself, says a religion expert who's confident we'll still be here on May 22.

Prof. Richard Ascough, who teaches an apocalyptic literature course at Queen's University's School of Religion, says Family Radio's international billboard campaign and mission play on a consistent human belief that the current generation is somehow unique.

"Throughout history, every generation has had… some interpretation that places the end times within their own generation," he told CTV.ca in a recent interview, days before doomsday as predicted by the fringe group. "I get the worrying sense from their material that they would be as surprised as their followers that they are still here May 22."

According to Family Radio's website, president Harold Camping discovered a mathematical formula that allowed him to find the day of the Rapture -- when Christians believe Jesus will return to Earth -- within the text of the Bible.

"It wasn't until a few years ago that the accurate timeline of history was revealed to true believers through the Bible," according to the group, which also predicted the world would end in 1994.

"On May 21, 2011 two events will occur… A great earthquake (that) will be so powerful it will throw open all graves. The remains of the all the believers who have ever lived will be instantly transformed into glorified spiritual bodies to be forever with God.

"On the other hand the bodies of all unsaved people will be thrown out upon the ground to be shamed. The inhabitants who survive this terrible earthquake will exist in a world of horror and chaos beyond description."

Family Radio has mounted an extensive campaign to share its discovery, posting thousands of billboards warning of the May 21 Judgment Day in cities throughout North America, including Toronto, Vancouver, Calgary, Saskatoon, Kingston and Quebec City. It has also organized missions to Iraq and Turkey, where volunteers are asked to use their final days on Earth handing out leaflets. RV caravans have been tasked with spreading the word across North America -- including one that will end its journey in Vancouver on the big day.

What makes this group different from others who have pushed a doomsday agenda, says Ascough, is that they don't seem to be asking followers to pay for the information that will save them -- although they do have a donation button prominently located on their website.

"They've used their radio ministry to build up substantial reserves which they are expending on this campaign," he said, noting he wouldn't be surprised if the group changed its message in the last days before May 21. "Other groups, as the time has gotten closer, say ‘we need to make the last push and we'll be able to put up more billboards. You're not going to need your money after that day.'"

He said another interesting aspect of Family Radio is that, while clearly a fringe Protestant group, it's not pushing a particular church.

"They say things like, ‘if you belong to a church it doesn't mean you will be saved because the churches have been teaching their followers the wrong thing all along.' They don't say you have to join a group, they say you really have to believe.

"(Groups like this) will tell their followers, 'because we proclaim the truth, the dominant groups will reject us just like people did with Jesus,'" he added. "We saw that with tragic consequences with (cult leader) David Koresh."

While Family Radio's Camping seems certain about the date of Judgment Day, Ascough says the Bible contains very little clear information to that effect. In fact, "Jesus and Paul said very clearly they don't know when the end times will be," he said, noting even the apostle Paul thought the Rapture would happen in his lifetime.

And while the idea of impending doom can seem like a joke to non-believers, it can have serious consequences. People who fall victim to such prophecies can become ensnared in cults or be coerced into giving up considerable sums of money.

Such rhetoric also adds to the atmosphere of fear in today's society, says Ascough, who points to former U.S. presidents Ronald Regan and George W. Bush as leaders who often used doomsday language when pushing for drastic measures.

"It must not have been more than 15 minutes after we knew what was going on about 9-11 that someone emailed me about how this fulfilled a Biblical prophecy about the end of the world," said Ascough. "I'm for free speech, but at the same time, we should always question the source of this material and look carefully at it."

A brief history of doomsday theology:

2nd Century BC: First documented predictions of an impending doomsday

400 – Apocalyptic scripture the Shepherd of Hermas is left out of the Biblical canon, while the Book of Revelation, previously excluded, makes the cut

1830s – Irish priest John Nelson Darby first preaches the idea of the Rapture, lays the foundation for much of modern end-times theology

1955 – God's judgment period begins, according to the Branch Davidians of Waco, Texas. They believed God was sorting through all dead and living souls to decide who would join him after the Rapture

1970 – Book "Late Great Planet Earth" compares end-times scenarios in the Bible to contemporary events (such as the birth of the state of Israel and the formation of the European Economic Community) to show the Apocalypse would occur during the "current generation"

March 26, 1997 – About 40 members of the Heaven's Gate cult, which believed aliens were coming to wipe Earth clean, commit suicide in San Diego, Cali.

May 21, 2011 – Doomsday promoted by California-based Family Radio in massive international campaign

Dec. 21, 2012 – A mistaken interpretation of the Mayan calendar has led to end times predictions for this date