Here are some conversations to illustrate the difference: 1. A: I went to the Ritz Hotel last night. B: Really, did you have dinner there? A: No, I just had some tea. This is talking about a past time. A: Have you had dinner? B: No, I haven't. I'm quite hungry, actually. This is talking about the present time - you're hungry because you haven't had dinner. 2. I saw this movie two years ago. This is talking about past time. I've seen this movie, so I don't want to see it again. I'd rather see another one. This is talking about the present time - you don't want to see this movie at the moment because you've already seen it.