Present perfect tense

Conclusion
In the previous sections tense has been discussed in terms of its general characteristics and its various uses in referencing present, past, and future time. As has been previously covered, tense is not a generic term for time in language nor is it the only time element with which linguists are concerned. Instead it is one of five universal attributes of language used to convey time information. The other attributes (aspect, mood, perfection, and aktionsart) are inherently tied to tense and the relationship of all five are so intertwined that each can rarely be discussed without consideration of all of them together.
Tense is however a very straight forward concept. It is purely a manner of expressing the contrast between two temporal references on the timeline of an utterance. The primary reference for determining tense is always the Time of Utterance (TUTT) — the point in time at which the utterance is actually said, heard, written, read, or otherwise communicated. Except for in cases of reported or quoted speech that happens in either the past or future, TUTT is always now (present). This makes it easy for determining the primary temporal reference because most of the time it’s present and thus doesn’t require further analysis. The position of the secondary temporal reference and its relative distance from TUTT is what actually determines tense. If the secondary reference occurs earlier than the primary reference (or visually, to the left of it) the tense of the utterance is past. Likewise, if it occurs after TUTT (or visually again, to the right of it), the tense is future. Unlike present tense which is absolute (it’s always now), past and future are not specific tenses but rather ranges. If the secondary reference is to the left of the primary but very close to it on the timeline, tense can be said to be immediate past. Likewise if were to the left but much farther away, it could be said to be distant past.
It is the interelation with aspect and aktionsart that determines which type of secondary temporal reference is used to establish tense. As stated above, the primary reference is always TUTT, and that Time of Utterance is almost always present because most utterances are communicated at the instant they are written, read, said, or heard (for instance, since you are just reading this, it’s being communicated to you now, thus its TUTT is now). The secondary reference can be either the Time of Assertion (TAST), Time of Evaluation (TEVL) or Time of Completion (TCOM). TUTT, TEVL, and TCOM are always punctular, meaning they have no duration and occupy only a single point on the timeline of the utterance. Depending on whether either the aspect of the utterance or the aktionsart of the inclusive verb are durational or not though, TAST can be either punctular or durative — occuring over a range of time along the timeline rather than a point. The various types of aspect and aktionsart are discussed in specific chapters to follow with a more detailed discussion of their effect on methods of determining tense.
Some resources describe tense as either relative or absolute, yet while the dual systems proposed are incorrect, there is some merit to this idea. The only absolute tense is the pure present which occurs when an utterance has a TUTT of ‘now’ coinciding with a TAST, TEVL, or TCOM of ‘now’. Even this expression of tense is not truly absolute in the sense of being locked, because if both temporal references where to move equally to the left of right along the timeline (say in reported speech), the tense of the utterance would still be present, even though the utterance itself has been moved into the future or past. It is thus much more rational to consider tense as relative to the time of utterance, and to think of the time of utterance as relative to now (the time of analysis for tense). This type of analysis can quickly become cumbersome and provides a good example of how descriptions of tense have become so disparate from language to language and conflated with other concepts over the years.
Finally, it should be remembered that tense is only this contrast between temporal references of the utterance described above. It is an attribute of an utterance as a whole and not any part within. Tense of an utterance can only be described in terms of present, past, and future, and degrees thereof. It is thus correct to say present tense, but not present perfect, present simple, or present progressive. Present perfect refers to the idea that an utterance is in present tense and is perfected (see Chapter 4 – Perfection); present simple refers to an utterance in the present tense, simple (a generic name for non-durational aspects) aspect, nonperfected; likewise present progressive refers to a non-perfected, durational aspect utterance in the present tense. These terms all refer to the same single tense however — the present.