The answer is July 16. Most of the explanations I've seen are hard to follow; here's my version of it.Albert and Bernard just became friends with Cheryl, and they want to know when her birthday is. Cheryl gives them a list of 10 possible dates.

May 15, May 16, May 19

June 17, June 18

July 14, July 16

August 14, August 15, August 17

Cheryl then tells Albert and Bernard separately the month and the day of her birthday respectively.

Albert: "I don’t know when Cheryl’s birthday is, but I know that Bernard does not know too."

Bernard: "At first I don’t know when Cheryl’s birthday is, but I know now."

Albert: "Then I also know when Cheryl’s birthday is."

So when is Cheryl’s birthday?

Suppose A were told the bday month were

**May**. This would leave the

**15**,

**16**and

**19**as possible dates. The 15 and 16 dates appear with other months, but if B were told the bday date was 19, then B would immediately know May 19 as the bday since there are no other 19 dates in the set of ten.

That is to say, if the bday month were May, there is a non-zero chance (1 in 3 to be exact, but all that matters is that it's non-zero) that B would know the bday from the day alone. But A in his first comment says he knows there is NO chance B knows the bday from the date alone. This means the assumption of May as the bday month is

**FALSE**.

One reaches a similar conclusion when assuming

**June**as the bday month (because June 18 is the only one with an 18 in it), so this month is also ruled out in similar fashion.

This leaves

**July**or

**August**as the bday month, and the date possibilities are

**14, 15, 16, 17**. We are told B knows which of these it is.

Let's suppose B were told the bday date is

**14**. But B says in his comment that he now knows from A's first comment the full bday date. But the 14 possibility has two different months attached to it: July and August. This means 14 cannot be the date, which leaves

**15, 16 and 17**as the bday date candidates, each of which have only one matching month and so all three remain as candidates; the three remaining possibilities are

**July 16**,

**August 15**and

**August 17**. Since B knows (was told) which of 15, 16, 17 is the bday date, he now knows the bday in full, consistent with his comment.

Now let's suppose the bday month is

**August**and consider A's second comment, in which says he has figured out the bday in full on the basis of B's remark. But there are two possibilities for August so this conclusion would be wrong. Therefore the bday cannot be in August.

This leaves the last remaining possibility of

**July 16**, which is the solution.

I wonder if the problems on the Wonderlic ever get this challenging?