Facebook's Mark Zuckerberg has just debunked a more-than-a-decade-old public notion about himself.

The chairman, chief executive officer and co-founder of the world's most popular social media platform is now saying he's not atheist.

In a post wishing everyone a "Merry Christmas and Happy Hanukkah," Zuckerberg answered a commenter who wondered why he made the greeting and asked him, "But aren't you atheist?"

Zuckerberg responded with a definitive "no," adding, "I was raised Jewish and then I went through a period where I questioned things, but now I believe religion is very important."

This contradicted his Facebook profile that at one point said he was an atheist before he removed his religious preference from his page, according to Patheos. The Wall Street Journal also alluded to his atheism in a 2007 story.

In the same Facebook thread, Zuckerberg even joked about religion.

When a commenter asked why Facebook doesn't notify that Dec. 25 is Jesus birthday, Zuckerberg replied: "You're not friends with Jesus on Facebook?"

Could it be that Zuckerberg had a change of mind on religion when he and his wife met Pope Francis in Vatican City last August?

No one could tell for sure. In a statement he posted on Facebook about that Vatican meeting, Zuckerberg said he and Pope Francis talked about efforts to help poorer communities connect to the Internet.

"We told him how much we admire his message of mercy and tenderness, and how he's found new ways to communicate with people of every faith around the world," wrote Zuckerberg.

Zuckerberg is not the first notable public figure in the United States to be tagged as atheist only to publicly deny it.

U.S. Senator and former Democratic Party presidential hopeful Bernie Sanders also found himself in the same situation and responded just like what Zuckerberg did.

"First of all, I am not an atheist," Sanders said last July in response to leaked emails claiming that he was an atheist and that it should be used against him to benefit Hillary Clinton.