There in a forest, a wolf and a fox. In every Monday, Tuesday and Wednesday, the wolf would only say lies (nothing of what he said was true these days), and other days he would only say truths.
While the fox said only lies in every Thursday, Friday and Saturday (nothing of what she said was true these days), and the rest of the day just spoke truths.
One day they met in the forest and the wolf said:
– Hello, Mrs. Fox. Yesterday I lied.
And the fox replied:
– Hello, Your Wolf. Yesterday I also lied.
Question: What was the day in which there was this conversation?