The billboards carry a stark message on a sunset backdrop: Judgment Day is coming May 21, 2011.
A fringe U.S. evangelical Christian group says it has erected some 2,000 ads around the world, including in 17 Canadian cities, advising of the Second Coming and salvation for true believers. Everyone else, it warns, will suffer a powerful earthquake and five months of hell on earth.
"The great amount of biblical signs and proofs absolutely guarantee that Judgment Day will begin on May 21 this year," the group, Family Radio, says on its website.
The warning is the latest in a long list of apocalyptic dates red-circled by extremist religious organizations.
The California-based group, which runs a Christian radio network, is not trying to raise funds or recruit followers - something Richard Ascough, a Queen's University religious studies professor, finds troubling.
"That scares me more. If they were asking for money, you'd know they're a fraud. And you could call them out on that. By not asking for money, I think they really and truly do believe," he said. "What's worrying about that is the effect that that could have on people who might think, 'Well, if I'm not going to be here, I may as well spend all my money, throw it away, give it away, whatever.'"
Followers said they are just following God's decree to warn others and that the best way is through a global advertising campaign.
"Believers are commanded to blow the trumpet, to sound the warning when the sword is coming upon the land. When you know this information … and you don't warn the people, then their blood will be upon your head," said Michael Garcia, a special projects co-ordinator for Family Radio.
Mr. Garcia and others believe there is still time to pray for salvation. The signs also advise: "Cry mightily unto God for His mercy."
Asked what would happen if May 21 does not mark the beginning of the end, Mr. Garcia would not countenance the possibility. "There are no question marks. God has given us all the proofs from the Bible. … It's going to happen."
Mr. Garcia estimates the group's billboards have been erected in more than 40 countries, including Turkey, Iraq, Mexico, Zimbabwe, India, Poland and Russia. In Canada, the ads have appeared in 17 cities from Halifax to Vancouver. He refused to disclose the cost, but the non-denominational, non-profit organization said it decided to use "all available resources" for the campaign.
Caravans of volunteers are also handing out pamphlets, mostly in the United States. A small contingent is scheduled to arrive in Calgary this Friday and Vancouver next Tuesday.
Harold Camping, Family Radio's president, came up with May 21, 2011, "from evidence found in the Bible," the website says. He determined that Christ's Second Coming would happen on that date, which he claims is the exact 7,000-year anniversary of Noah escaping destruction from the floods.
Dr. Ascough and other scholars scorn such calculations, saying that biblical texts use symbolic language and don't contain secret codes about the date of the end of the world.
Mr. Camping has been wrong before. He wrote a book predicting the world would end in 1994. Family Radio now says that "important subsequent biblical information" was not known at the time.
Apocalypse whenever: Other predictions for the end of the world
William Miller, a Baptist preacher who founded the Millerite movement, which eventually became the Seventh Day Adventist denomination, thought the Second Coming would happen between 1843 and 1844.
Charles Russell, founder of what became the Jehovah's Witnesses, predicted that Christ would return invisibly in 1874 and then physically in 1914.
Some people believe the world will end on Dec. 21, 2012, according to the ancient Mayan calendar.