The Present Perfect of English is a linguistic curiosity, especially when viewed in light of equivalent tenses across other Indo-European languages. The basic meaning, independent of context, is that of an event which happened sometime in the past and continues to have present relevance. Usually, this refers to something in the recent past. In the sequence I have walked, I walked, I had walked - I have walked seems closest to the present moment. That does not apply in all contexts, however. For example, one could write an astrophysical explanation that read The Big Bang has caused the universe to expand for several billion years. This event occurred as far back in time as one could go, but it still has present relevance (the universe is still expanding). Such a meaning holds for the present perfect tenses in other languages as well.

English, however, exhibits a noteworthy difference. One cannot use a past-time adverb such as last week or a year ago with the Present Perfect in standard English. Other languages place no such limits on adverb usage with the Present Perfect. In Norwegian, it's perfectly acceptable to write such a sentence as Vi har sett dem for et øyeblikk siden, or literally We have seen them a moment ago. Another example from Finnish (care of vuo): En ole häntä nähnyt nyt tässä, literally "I have not seen him now." In this case, 'now' refers to the general now of the surrounding circumstances and not necessarily the very present moment. This applies to other languages with an equivalent present perfect tense. English's restrictions on the Present Perfect are cross-linguistically unusual.

Since past-time adverbs may not be used with the Present Perfect, one might conclude that the present perfect tense in English is not really a past tense at all, but rather a present tense referring to a past event. Basically, making the 'present relevance' aspect of the tense more important than the 'past event' aspect. Upon closer examination, however, this explanation doesn't fit the actual use of the Present Perfect. If you were to ask someone Have you seen John recently?, s/he could respond I have seen him recently, but not today. Recently is a past-time adverb, and more importantly, it is incompatible with a present tense.

So, why recently, but not yesterday? The key is that recently extends right up to the present; it is a past-time adverb with present relevance. A different answer to the same question posed above might be Yes, I've actually seen him this morning. If it was the afternoon, this sentence would not be possible (Yes, I have seen him this morning, but not since then ...?), however if it is still the morning, the past-time adverb also has present relevance. It was morning when the event occurred, and it is also morning now. So, the English Present Perfect, which refers to events in the past that have present relevance, may only be used with adverbs that also refer to the past, but have present relevance.

It would be wonderful if this neat summary covered all bases, but languages are slippery. Many dialects of English do allow exclusively past-time adverbs to be used with the Present Perfect. And what about sentences such as I've not seen him now? Now is certainly an exclusively present-time adverb, and yet that sentence does not seem entirely implausible. One might object that now in this case is a short-hand for up to now, thus incorporating a past element. That would solve the problem, but it leaves the question open as to why up to now and now are entirely separate adverbs in every other context. But these exceptions are obscure and on the borderlines of incorrect speech, occupying that fuzzy ground between the real language in its everyday use (not the written language) and idiosyncratic human errors.

With general satisfaction, one can define the English present perfect tense as a past tense indicating present relevance, restricting itself to adverbs of a similar form.