Camping, who was then president of the Family Radio Christian network, claimed the Bible as his source and said May 21 would be the date of the rapture and the day of judgment "beyond the shadow of a doubt".

On May 23, Camping stated that May 21 had been a "spiritual" day of judgment, and that the physical rapture would occur on October 21, 2011, simultaneously with the destruction of the universe by God.

[16] In March 2012, Camping "humbly acknowledged" in a letter to Family Radio listeners that he had been mistaken, that the attempt to predict a date was "sinful", and that critics had been right in pointing to the scriptural text "of that day and hour knoweth no man".

"[17] Camping presented several arguments labeled "numerological" by the mainstream media,[24] which he considered biblical proofs, in favor of the May 21 end time.

A civil engineer by training, Camping stated he had attempted to work out mathematically based prophecies in the Bible for decades.

[31] Camping's rapture prediction, along with some of his other teachings and beliefs, sparked controversy in the Christian and secular Western worlds.

Theology professor Matthew L. Skinner, writing at the Huffington Post, noted the "long history of failed speculation" about the end times and cautioned that end-of-the-world talk can lead Christians to social passivity instead of "working for the world's redemption".

[36][37] A group of Christians set up a website called RaptureFail with the stated intention of undermining "this embarrassment to the Body of Christ.

"[38] Evolutionary biologist and atheist Richard Dawkins dismissed Camping's prediction, writing that "he will inevitably explain, on May 22, that there must have been some error in the calculation, the rapture is postponed to ... and please send more money to pay for updated billboards.

"[39] California Director of American Atheists Larry Hicock said that "Camping's well-intentioned rapture campaign is indicative of the problems with religion".

[40] In 2010, Marie Exley of Colorado Springs made news by purchasing advertising space in her locality, promoting the alleged rapture date on a number of park benches.

[41] After that, more than 5000 "Judgment Day" billboards were erected in locations across the world, including the Dominican Republic, Ethiopia, Ghana, Indonesia, Israel, Jamaica, Jordan, Lebanon, Lesotho, the Philippines, Tanzania and the United States.

[45] Family Radio spent over US$100 million on the information campaign, financed by sales and swap of broadcast outlets.

Five recreational vehicles announcing on their sides that Judgment Day was to begin on May 21, 2011, were sent out from their headquarters in Oakland, California, to Seattle, Washington.

[53] About 5,000[24] ethnic Hmong gathered at a remote town in Vietnam's Mường Nhé District in Điện Biên Province in early May, where they planned to await the arrival of Christ.

[54] Pastor Doan Trung Tin indicated that a translated version of Camping's prediction had influenced about 300 of his parishioners to go to the assembly point, selling their belongings to be able to afford the journey via bus.

[63] On May 23, he returned to his Open Forum radio program, with members of the press in attendance, and, departing from his typical format, took questions from the reporters present instead of from callers.

[64] He stated that May 21 had been an "invisible judgment day" which was purely spiritual in nature, and that he now realized that the physical rapture would take place on October 21, simultaneously with the destruction of the universe.

"[66] Responding to a question, Camping said his organization would not return money donated by followers to publicize the May 21 prediction, saying "We're not at the end.

[68]A Family Radio staffer suggested that the delay might be God's way of separating true believers from those willing to doubt the "clear biblical warnings.

"[13] Individual followers who had spent time and money promoting Camping's prediction were "crestfallen" after May 21 passed without evidence of the rapture.

[70] A group from the Calvary Bible Church in Milpitas, California offered a session to comfort those who had believed in the prophecy.

[75][76] On May 21, groups of protesters gathered at Family Radio's headquarters in Oakland to mock the evangelical broadcaster's failed prediction.

One group released human-shaped helium balloons to simulate souls rising to heaven,[77] while another person played The Doors' song "The End" over a boombox.

[15] Sometime after October 21, Family Radio posted an audio message from Harold Camping on their home page.

As October 21 approached, the Freedom from Religion Foundation bought space on more than 40 billboards in the Bay Area to mock Camping's predictions and urge viewers to use rational judgment.

The decision was made as part of an effort to both move away from Camping's theology, and to reintroduce programs from outside ministries into the network's schedule.