What if A, B, and D are liars and C is telling the truth. It is the only straight forward answer. Why does saturday have to be the day just because 2 people intimated that it was? If i were on and island and asked 4 people he same question survival and instinct and logic tell me to go with the guy that is not talking in circles to me. Honest people wouldn't do that. THE DAY IS FRIDAY

This puzzle is real good. I got the right answer but for the wrong reason until I read some of the other posts.

The key is the problem states: "Because everything you need to know is how many people lied, I will not tell. What day of the week was it?"

If A B and D are liars then the number of liars (the only thing you need to know to get the right answer) is 3. But if we know there are three liars, there are two possible solutions. If A B and D are liars than the answer would be Friday. But B C and D could also be liars, making the answer Thursday. So there can't be 3 liars, or we would need more information to determine which 3 where the liars and the statement specifically says we only need the number of liars to get the correct answer.

So, given only the number of liars and the information in the problem the answer has to be Saturday, because it is the result of 2 people being liars producing a unique result, while all other counts for liars would produce non-unique answers.