2016.07.08
Albert and Bernard just met Cheryl. "When's your birthday?" Albert asked Cheryl.
Cheryl thought a second and said, "I'm not going to tell you, but I'll give you some clues." She wrote down a list of 10 dates:
May 15 - May 16 - May 19
June 17 - June 18
July 14 - July 16
August 14 - August 15 - August 17
"My birthday is one of these," she said.
Then Cheryl whispered in Albert's ear the month - and only the month - of her birthday. To Bernard, she whispered the day, and only the day.
"Can you figure it out now?" she asked Albert.
Albert: I don't know when your birthday is, but I know Bernard doesn't know, either.
Bernard: I didn't know originally, but now I do.
Albert: Well, now I know, too!
When is Cheryl's birthday?