Classification of tenses

Tenses can be broadly classified as:

* absolute: indicates time in relationship to the time of the utterance (i.e. "now"). For example, "I am sitting down", the tense is indicated in relation to the present moment.
* relative: in relationship to some other time, other than the time of utterance, e.g. "While strolling through the shops, she saw a nice dress in the window". Here, the "saw" is relative to the time of the "strolling". The relationship between the time of "strolling" and the time of utterance is not clearly specified.
* absolute-relative: indicates time in relationship to some other event, whose time in turn is relative to the time of utterance. (Thus, in absolute-relative tense, the time of the verb is indirectly related to the time of the utterance; in absolute tense, it is directly related; in relative tense, its relationship to the time of utterance is left unspecified.) For example, "When I walked through the park, I saw a bird." Here, "saw" is present relative to the "walked", and "walked" is past relative to the time of the utterance, thus "saw" is in absolute-relative tense.

Moving on from this, tenses can be quite finely distinguished from one another, although no language will express simply all of these distinctions. As we will see, some of these tenses in fact involve elements of modality (e.g. predictive and not-yet tenses), but they are difficult to classify clearly as either tenses or moods.

Many languages define tense not just in terms of past/future/present, but also in terms of how far into the past or future they are. Thus they introduce concepts of closeness or remoteness, or tenses that are relevant to the measurement of time into days (hodiernal or hesternal tenses).

Some languages also distinguish not just between past, present, and future, but also nonpast, nonpresent, nonfuture. Each of these latter tenses incorporates two of the former, without specifying which.

Some tenses:

* Absolute tenses
o Future tenses. Some languages have different future tenses to indicate how far into the future we are talking about. Some of these include:
+ Close future tense: in the near future, soon
+ Hodiernal future tense: sometime today
+ Post-hodiernal future tense: sometime after today
+ Remote future tense: in the more distant future
+ Predictive future tense: a future tense which expresses a prediction rather than an intention, i.e. "I predict he will lose the election, although I want him to win". As such, it is really more of a mood than a tense. (Its tenseness rather than modality lies in the fact that you can predict the future, but not the past.)
o Nonfuture tense: refers to either the present or the past, but does not clearly specify which. Contrasts with future.
o Nonpast tense: refers to either the present or the future, but does not clearly specify which. Contrasts with past.
o Not-yet tense: has not happened in present or past (nonfuture), but often with the implication that it is expected to happen in the future. (As such, is both a tense and a modality). In English, it is expressed with "not yet", hence its name.
o Past tenses. Some languages have different past tenses to indicate how far into the past we are talking about.
+ Hesternal past tense: yesterday or early, but not remote
+ Hodiernal past tense: sometime earlier today
+ Immediate past tense: very recent past tense, e.g. in the last minute or two
+ Recent past tense: in the last few days/weeks/months (exact definition varies)
+ Remote past tense: more than a few days/weeks/months ago (exact definition varies)
+ Nonrecent past tense: not recent past tense, contrasting with recent past tense
+ Nonremote past tense: not remote past tense, contrasting with remote past tense
+ Prehesternal past tense: before hesternal past tense
+ Prehodiernal past tense: before hodiernal past tense
+ Preterit: past tense not marked for aspect or modality
o Present tense
o Still tense: indicates a situation held to be the case, at or immediately before the utterance
* Absolute-relative tenses
o future perfect tense: will have completed by some time in the future, will occur before some time in the future
o future-in-future tense: at some time in the future, will still be in the future
o future-in-past tense: at some time in the past, will be in the future
o future-perfect-in-past tense: will be completed by some time which is in the future of some time in the past, eg., Sally went to work; by the time she should be home, the burglary would have been completed.
o past perfect tense: at some time in the past, was already in the past
* Relative tenses
o relative future tense: is in the future of some unspecified time
o relative nonfuture tense: is in the past or present of some unspecified time
o relative nonpast tense: is in the present or future of some unspecified time
o relative past tense: is in the past of some unspecified time
o relative present tense: is in the present of some unspecified time
http://en.wikipedia.org/wiki/Grammatical_tense