(See also Present Perfect: Form)
The Present Perfect is a form of the verb which combines a view of a situation that occurred, or at least began, in the past and which has some bearing on the present. Many grammars list the different ways in which this tense is used; some of the more common appear below. Students may find it less confusing to consider this tense as a retrospective aspect. This is discussed later in the article.
Uses – traditional list
1. A situation begun in the past and continuing through the present:
My flatmate has lived in Prague since 1998.
2. A situation begun in the past and continuing up to the present, but not beyond:
Hello, Neil. I haven’t seen you for ages.
3. A past action occurring within a time period considered still to be continuing:
Peter has called me four times today.
4. A situation occurring at an unspecified past time that has current relevance:
I’ve already eaten. (the implication being that I do not wish to eat now)
5. Actions occurring in the very recent past (often with just:
The Bensons have just arrived.
6. Future time and conditional clauses:
We can leave when Paul has finished.
Some uses appear connected, but learners might be forgiven for wondering how they could know which was meant. Fortunately, as with other tenses and aspects, there is a simpler explanation.
The Present Retrospective Aspect
We use the Present Retrospective Aspect when we look back from the present moment to a situation that began in the past, and is connected in some way to the present time.
We can see the application of this in the examples given above:
1. My flatmate has lived in Prague since 1998.
2. Hello, Neil. I haven’t seen you for ages.
3. Peter has called me four times today.
4. I’ve already eaten.
In these first four examples we clearly have situations, living, not-seeing, calling and eating that began prior to the time of retrospection - the present moment. It is equally clear that the situations are connected to the time of retrospection. In  –  the time period extends from the past to that time. In , the connection is that I at the time of retrospection, am not hungry. This, or some similar present consequence of a past situation, will be clear from the context. Whether the situation continues up to, or through, the time of retrospection will be clear from the context.
5. The Bensons have just arrived.
In  the situation is, in the speaker’s mind, so close to the present that this closeness/vividness is the connection. However, the fact is that the situation however recent, actualised in the past, and speakers can choose to distance it in time:
5a. The Bensons just arrived.
Speakers of BrE tend to view such recent past situations retrospectively ; AmE speakers tend to distance them [5a]. The same is true when already, yet, recently and expressions of present time periods such as today, this morning, etc. are used.
6. We will leave when Paul has finished.
Here the time of retrospection, the time of our leaving, is future and the actualisation of the future situation looked back on is before that time. Depending on the situations foreseen, there may be little difference in the length of time between the finishing and the leaving in  and in [6a]:
6a. We will leave when Paul finishes.
However, in , the speaker has chosen to see the leaving as actualising at the end of a time period, however short, after the finishing. In [6a], the situations could be seen as actualising at the same time.
- Lewis, Michael (1985) The English Verb, Hove: LTP