Present perfect или simple past?

It is often possible to use the present perfect (I have done) or the simple past (I did):

  • I've lost my key. Have you seen it anywhere?
    or: I lost my key. Did you see it anywhere?

But do not use the present perfect to say when something happened (for example, yesterday,
two years ago, when I was a child
, etc.). Use a past tense in these sentences:

  • I lost my key yesterday. (not have lost)

  • Did you see the movie on TV last night? (not have you seen)

  • I ate a lot of candy when I was a child. (not have eaten)

Use a past tense to ask when orwhat time something happened:

  • What time did they arrive? (not have they arrived)

  • When were you born? (not have been born)

Do not use the present perfect (I have done) for happenings and actions that are not connected with the present (for example, historical events):

  • The Chinese invented printing. (not have invented)

  • How many symphonies did Beethoven compose? (not has... composed)

Now compare these sentences:

Present perfect (I have done)

I've smoked 20 cigarcttes today.

Today is a period of time that continues up to the present. It is not a finished time. So we use the present perfect.

Dan hasn't been sick this year.
Have you seen Ann this morning?
(It is still morning.)
Have you seen Ann recently?
We've been waiting for an hour. (We arу still waiting.)
Pierre has lived in Quebec for six years.
(He still lives there.)
I have never played golf (in my life).

The present perfect always has a connection with the present.

Simple past (I did)

I smoked 20 cigarettes yesterday.

Yesterday is a finished time in the past. So we use the simple past.

Dan wasn't sick last year.
Did you see Ann this morning?
(It is now afternoon.)
Did you see Ann last week?
We waited (or were waiting) for an hour. (We are no longer waiting.)
Pierre lived in Quebec for ten years.
(He no longer lives there.)
I didn't play golf when I was on vacation last summer.

The simple past tells us only about the past.