Uhm, nope, I think it's from a book that's used to teach a class in Singapore, if I remember correctly. They just don't use past tense in the exercise, but I've seen that before, especially in maths. Can you work it out?

Too should be either, right?

I'm extremely tired at the moment, but I narrowed it down to July 16, August 15 or August 17. I'll probably fall asleep right about now.

I'm getting the strong impression that, if both of them are smart enough, you can't narrow it down further.
Eyes burning, pressing post reply and closing them.

well of those three dates, which of them would, if alfred knows the month, let him know the answer?

July 16th,

since Albert says Bernard does not know it cannot be a single day month, so July or August. Since Albert infers that, and says he knows, it cannot be a repeat number day, so July 16th, August 15th, August 17. Now since Bernard says he knows it has to be the single month, because if it were August he would not in fact know. July 16th.

This is a 2-strand logic string, and not a very hard one. There are some communities online that are dedicated to logic puzzles that can be 4 or 5 strand. I saw this in class yesterday (our teacher got bored) and even the class goof got it.

sorry if my explanation were confusing, but I basically left out a few commas

you mixed up the names JY but yea that's right.

july 16:
a: "i'm not sure, b doesn't know for sure"
b: "oh, then i know it"
a: "oh, me too"

august 15/17:
a: "i'm not sure, b doesn't know for sure"
b: "oh, then i know it"
a: "i'm still not sure"

let me reiterate:

Albert knows the day, Bernard knows the month. Since Bernard says that 'he knows Albert doesn't know' it means It isn't a month that has the 18th or 19th (which are the only ones not repeated) Now Albert says that 'he knows' so it has to be A day in July or August and it cannot be the 14th, because that is repeated and Albert would otherwise be unsure. Bernard now knows that BECAUSE Albert knows what the exact date is, he realizes it cannot be the 14th (or else Albert would not know). Bernard knows the month, and since he says that (in the last comment) he now knows, it is the July 16th, the only 'single' day that is left in a month.

people get confused because they start to think (after step 1) that Bernard is as in the dark as they are. You need to realize Cheryl is actually talking to 3 people. Bernard, Albert, and You, the reader

July 16th I believe.

If Albert knows that Bernard doesn't know then you can rule out any month with a unique day. So there goes May and June

As soon as Albert says that Bernard is able to figure this out.

The days left are July 14th and July 16th as well as Aug 14th, Aug 15th, and Aug 17th.

The 14th of both months is out since it would prevent Bernard from figuring it out

So down to July 16th, Aug 15th, and Aug 17th.

Now here, we know that by getting to this point that Bernard would be able to figure out the date no matter what. But the only way Albert can also know is if he knows the month will only have 1 option remaining, which means the 16th of July.

Cheryl ought to be less obtuse. She'll never find a husband with that attitude.

Albert says "I don't know when Cheryl's brithday is, but I know that Bernard does not know too.", and then later says "then I also know too" after Bernard tells him that "At first I didn't know when Cheryl's birthday is, but I know now."

Well, going from that it seems like Bernard knew when cheryl's birthday is immediately after she'd told him the day- He didn't know before then, but now he does. There fore it must be either the 19th of May or the 18th of June. Once Albert learns this, he knows the birthday since he already knew the month (either May or June) and know he knows it's whichever day is unique (19th or 18th).

Also, when Albert says "I know Bernard doesn't know" it could just be bad grammar when they meant to say "I think Bernard doesn't know". How would he know Bernard doesn't know?!

Very well arborinius, you are the only one who solved this riddle!