LOS ANGELES - The evangelical Christian broadcaster whose much-ballyhooed Judgment Day prophecy went conspicuously unfulfilled on Saturday has a simple explanation for what went wrong - he miscalculated.

Instead of the world physically coming to an end on May 21 with a great cataclysmic earthquake, as he had predicted, Harold Camping, 89, said he now believes his forecast is playing out "spiritually," with the actual apocalypse set to occur five months later, on October 21.

Camping, who launched a doomsday countdown in which some followers spent their life's savings in anticipation of being swept into heaven, issued his correction during an appearance on his "Open Forum" radio show from Oakland, California.

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The headquarters of Camping's Family Radio network of 66 US stations had been shuttered over the weekend with a sign on the door that read, "This Office is Closed. Sorry we missed you!"

During a sometimes rambling, 90-minute discourse that included a question-and-answer session with reporters, Camping said he felt bad that Saturday had come and gone without the Rapture he had felt so certain would take place.

Reflecting on scripture afterward, Camping said it "dawned" on him that a "merciful and compassionate God" would spare humanity from "hell on Earth for five months" by compressing the physical apocalypse into a shorter time frame.

But he insisted that October 21 has always been the end-point of his own End Times chronology, or at least, his latest chronology.

The tall, gaunt former civil engineer with a deep voice and prominent ears has been wrong before. More than two decades ago, he publicly acknowledged a failed 1994 prophecy of Christ's return to Earth.

To publicize his latest pronouncement, the Family Radio network posted over 2,000 billboards around the country declaring that Judgment Day was at hand, and believers carried the message on placards in shopping malls and street corners.

Asked what advice he would give to followers who gave up much or all of their worldly possessions in the belief that his Judgment Day forecast would come true, Camping drew a comparison to the nation's recent economic slump.

"We just had a great recession. There's lots of people who lost their jobs, lots of people who lost their houses ... and somehow they all survived," he said.

"People cope, he added. "We're not in the business of giving any financial advice. We're in the business of telling people maybe there is someone you can talk to, and that's God."