The evangelical broadcaster who left followers crestfallen by his failed prediction that last Saturday would be Judgement Day says he miscalculated.
Harold Camping said it had "dawned" on him that God would spare humanity "hell on Earth for five months" and the apocalypse would happen on 21 October.
Mr Camping said he felt "terrible" about his mistake.
But he said he could not give financial advice to those who spent their life savings in the belief the end was nigh.
Mr Camping had predicted that on 21 May, true believers would be swept up to heaven while a giant earthquake would bring destruction for those left behind.
His independent ministry, Family Radio International, spent millions of dollars on broadcasts, billboards and campaign vehicles to publicise the prediction.
Some followers donated their life savings or simply gave away their worldly possessions as the day approached.
Many expressed bewilderment and shock as the day came and went with no sign of the global cataclysm.
"I've been mocked and scoffed and cursed at," said Jeff Hopkins, a retired TV producer in New York state who spent some of his savings customising his car to showcase Mr Camping's warning.
"It's like getting slapped in the face."
Mr Camping had not been seen since Saturday until he appeared on a show on his Open Forum radio show, broadcast from Oakland, California, on Monday to give a 90-minute sometimes rambling presentation that included a question-and-answer session with reporters.
He said that when his prediction had failed to materialise he felt so terrible that he took refuge in a motel with his wife.
He said sorry for not having the dates "worked out as accurately as I could have".
Over the weekend, he said, he had returned to the scripture and it had "dawned" on him that a "merciful and compassionate God" would spare humanity by compressing the apocalyptic destruction into a shorter time frame.
But he insisted 21 October had always been the end-point of his own chronology - or at least his own latest chronology, as a previous prophecy that the apocalypse would strike in 1994 also failed to come to pass.
Asked if he had any advice to offer those who had given away their material wealth in the belief the world was about to end, Mr Camping said they would cope.
"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.
"We're not in the business of giving any financial advice," he added.
"We're in the business of telling people maybe there is someone you can talk to, and that's God."