You guys really liked Cheryl’s birthday brain teaser and left some pretty hilarious comments (and the answer) over at our Facebook post, but today, we have an even tougher problem for you: Denise’s birthday!

Albert, Bernard and Cheryl recently became friends with Denise, but Denise flat out refuses to tell them when her birthday is. Instead, she gives them a list of 20 possible dates, and tells the month to Albert, the day to Bernard, and the year to Cheryl. Here are the 20 dates:

Albert: “I don’t know her birthday, but I know Bernard doesn’t know.”
Bernard: “I don’t know her birthday, but I know Cheryl doesn’t know.”
Cheryl: “I don’t know her birthday, but I know Albert doesn’t know.”
Albert: “Now I know when Denise’s birthday is.”
Bernard: “Now I know too.”
Cheryl: “Me too.”

Please note that you will need a pen, a piece of paper, and an eraser to solve this problem.

As with last time, argue over at the Facebook post for this article.