1. I didn't see you for a long time.

2.I haven't seen you for a long time.

Let us assume that you didn't see this person for a couple weeks and accidently you saw the person today.

Which is the correct sentence to use in this situation.

What is wrong with the first sentence?
The second sentence borders present perfect tense, I think.
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The first sentence can imply that you were actively seeking the person out (such as in a picture or a crowded room), and it took you an extended period of time to find them.
I thank everybodyfor their contribution.

3. I didn't see see you since last summer.

4. I haven't seen you since last summer.

What is the proper one out of the above two sentences? I saw the person in question somewhere during last summer. Now almost after 6 months, I saw the person and said hello.

I know it is improper to use the present perfect sentence for a past event. For example, I have met him yesterday is wrong. It should be I met hime yesterday.

When there is a time frame, I guess both of the above sentence are fine. It could be last summer or summer 2000.

What would you right when there is an obvious time frame?
Sentence 4, Andrei.

We use the present perfect for something that began in the past and is still true today.

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