There are 24 shopping days left till Christmas.

And 171 days left until Jesus' second coming.

That's the message on 40 billboards around Nashville, proclaiming May 21, 2011, as the date of the Rapture. Billboards are up in eight other U.S. cities, too.

Fans of Family Radio Inc., a nationwide Christian network, paid for the billboards. Family Radio's founder, Harold Camping, predicted the May date for the Rapture.

Their message is simple — "He Is Coming Again" — and their aim is to get unbelievers to turn around quickly. But critics say the billboards are a waste of time, one more failed attempt to predict the end of the world.

The Rapture is going to be a great day for God's people but awful for everyone else, said Allison Warden, 29, who orchestrated Nashville's billboard campaign. She's a volunteer with WeCanKnow.com, a website set up by followers of Family Radio. She and other fans designed the billboards, along with T-shirts, bumper stickers and postcards to get Camping's predictions out.

Warden traveled from her home in Raleigh, N.C., to Nashville last week to check out the billboards, purchased through the end of the year. She wouldn't say how much they cost or name who paid for them.

She is absolutely sure that Camping's prediction is right.

"It's a certainty," she said.