How to tell if someone wants you to leave?

Sometimes when I visit my friends' houses, they ask me at what time I will be leaving. They would say something like, "Not trying to be rude, but what time are you leaving?" or "When are you leaving? The traffic is going to get worse." When I tell them that I will leave at a certain time (let's say 7:30 PM, for example), I noticed that some of my friends would say something like, "Hey, it's 7:30" when the time comes. Personally, I found this quite disrespectful and offensive, since I took it as a polite way to say, "Hey, it's 7:30. Leave now!" For me, that's a sign of horrible hospitality. I may be overreacting, but are there any ways to tell if someone wants you to leave? FYI, I'm really interested in reading body languages and interpreting people's minds.