April truth event

There are two groups known as the liars.

There is a group which can lie and can say the truth on either days. Friday, Saturday only, but it seems to have an info that one of them doesn't lie, if the group knew that he doesn't lie, he will be kicked out.

The other group seems to be more and more evil that they lie on the whole month of April, but not only that, on the rest of the year they lie on the whole weeks except the second week of all the month. If they knew that someone is lying on the other group that he is not lying with them they will tell the full group about it.

It was the second week of April but this benefited the boy because of something.

The second group already knew and said as follows as they didn't want to help him because they didn't know that the other group are liars but it was a very special day!

The following dialog took place for persons 1, 2, 3, 4:
1) He did not the the truth.
2) He is a liar.
3) I don't have something to say.
4) Liar.

Who said a lie!