"I wouldn't give him the time of day"

... is a common expression of scorn, but what exactly does it mean? ... I used to think it meant telling someone what time it was in response to a question: if you liked the person who asked, you would oblige and if not, you would ignore him. But the expression goes far back beyond the time when people wore watches... In Shakespeare's day, the meaning was quite clear. "Good time of day" or "fair time of day" was a salutation just like "good morning" or "good evening"...We no longer greet people by saying "good time of day," but we still use the idea of giving such a greeting as a sign of favorable attention. In other words, refusing to give someone the time of day is thinking so little of him that you would not say hello to him on the street." (credit to Scribal Terror)