The Douglas siblings live near each other in Brooklyn, and Mr. Douglas said he could not wait until Sunday — “I’m going to show up at her house so we can have that conversation that’s been years in coming.”

Ms. Douglas, who has a 7-year-old, said that while her family did not see the future the way she did, her mother did allow her to put a Judgment Day sign up on her house. “I never thought I’d be doing this,” said Ms. Douglas, who took vacation from her nanny job this week but did not quit. “I was in an abusive relationship. One day, my son was playing with the remote and Mr. Camping was on TV. I thought, This guy is crazy. But I kept thinking about it and something told me to go back.”

Ms. Douglas and other believers subscribe to the prophecy of Harold Camping, a civil engineer turned self-taught biblical scholar whose doomsday scenario — broadcast on his Family Radio network — predicts a May 21, 2011, Judgment Day. On that day, arrived at through a series of Bible-based calculations that assume the world will end exactly 7,000 years after Noah’s flood, believers are to be transported up to heaven as a worldwide earthquake strikes. Nonbelievers will endure five months of plagues, quakes, wars, famine and general torment before the planet’s total destruction in October. In 1992 Mr. Camping said the rapture would probably be in 1994, but he now says newer evidence makes the prophecy for this year certain.

Kevin Brown, a Family Radio representative, said conflict with other family members was part of the test of whether a person truly believed. “They’re going through the fiery trial each day,” he said.