You are not the only person to be confused by the present perfect. It is used more or less in the same way in English and Spanish, but there are some differences which make it the one thing English teachers here hate to teach!Originally Posted by endeavor6636
The diagram is ok, but does not really tell you "how" to use the present perfect. The explanation my students seem to be happier with is that this is the tense we use to talk about 1) experiences or actions which have happened "up to now", and 2) experiences or actions which happened at some time in the past but which "have an effect on" the present. It is also important to remember that tense and time are not necessarily the same thing. I really believe very strongly that the best way to understand the present perfect tense is to find as many examples of it being used as possible.
Some examples on 1) above:-
I have visited Madrid. This happened at some time in the past. I may have visited Madrid many times or just once. The important thing is I use the present perfect tense because I am saying that I have visited Madrid in the past but that does not mean I will not visit Madrid again. So I am talking about up to now in my life. If I used the past simple tense "I went to Madrid" then I am usually saying I visited Madrid and consider that as a single action in the past. It makes it easier to understand if you relate both examples to the time expressions you mentioned. I have visited Madrid 10 times (in my life up to now); I visited Madrid 10 times in 2003.
Other examples:- I have studied English for 6 years (up to now in my life); I studied English for 6 years (I am not studying English now). I have lived in Barcelona for 3 years (up to now); I lived in Barcelona for 3 years (now I live somewhere else).
Your example of the lost key is a good one for the second use of the present perfect I mentioned above. If you used the past perfect "I lost my key", then it is a single action which happened in the past and is finished. You could use a time reference like last year/yesterday/in 1997. If you use the present prefect "I have lost my key", then it is something that happened in the past, but you could not use the same time expressions (probably because you do not know when you lost it), and the loss of the key has an effect in the present - "so how am I going to get into my house!?"
I hope this helps - but experience suggest it may just confuse you more. The best way really is to search for grammar sites which give as many examples of the similar sentences using both past simple and present perfect so the meaning becomes easier. Good luck!