The writer has joked that the foretold end of the world has been put on hold in favour of the inaugural Fables convention.
"We've cancelled the Mayan Apocalypse! Again: We've cancelled the Mayan apocalypse!" he wrote on Twitter.
"The world will not end on December 21 of this year. After guaranteeing full refunds to those who attend Fablescon if the world did end, our financial people told us we couldn't afford the loss. Our only other choice was to cancel the end of the world. So we did.
"We worked closely with the Mayans, the Fates, Al Gore and the Gods of Destruction, reached a deal, after massive negotiations.
"This is just one more example of the lengths we will go to, to make sure you have a great time at Fabletown and Beyond. Did the San Diego Con cancel the world's destruction for you? No, they didn't. Did any other convention do this? No, they didn't. Only Fablescon takes that extra caring step and goes the extra mile for you. Maybe you should consider attending."
Willingham had previously teased an important announcement for yesterday.
Fablescon will be held in Rochester, Minnesota, from March 22 to March 24, with guests including Mike Carey, Kurt Busiek, Anthony Del Col, Conor McCreery, Peter Gross, Gene Ha and Chris Roberson.