There was a question recently in an email distribution list at work regarding the grammatical tense. Specifically, someone asked what we'd call "past", "present" and "future" in Inuktitut. Though it seems rather mundane at the surface of it, it is actually a very profound question on the nature of the human experience.
Grammatical tense (ie, past, present and future) is actually more than the three most obvious ones. Actually, the notion of "tense" belongs to a rather amorphous grammatical category of the verb that encompasses not only tense, but also aspect and mood/modality:
In many language descriptions, particularly those of traditional European linguistics, the term tense is erroneously used to refer to categories that do not have time reference as their prototypical use, but rather are grammaticalisations of mood/modality (e.g. uncertainty, possibility, evidentiality) or aspect (e.g. frequency, completion, duration). (http://en.wikipedia.org/wiki/Grammatical_tense*)
*the Wikipedia entry on "grammatical tense" is rather poorly done and should be taken with a grain of salt, though it's serviceable enough to give one an idea of it...
I wouldn't go so far as to say that the notion of tense has been used "erroneously" but rather "amorphously", and naturally so: "tense", "aspect" and "mood/modality" are subcategories of verb quality - whether denoted grammatically, morphologically, syntactically, all human languages have this functional (and refinable) notion and, at least, a cursory reading of Kant's philosophy suggests that we cannot transcend this need to frame our linguistic references in describing act/fact/propositional.
Besides, "past", "present" and "future" there is "perfective" and "imperfective" (again, quoting Wikipedia):
Tense differs from aspect in showing the time reference, while aspect shows how the action/state is "envisaged" or "seen" as happening/occurring [ie, linguistically described]. The most common aspectual distinction in languages of the world is that between perfective (complete, permanent, simple, etc.) and imperfective (incomplete, temporary, continuous, etc.). (ibid)
perfective = [-sima-]; [-janga/jara/jait]*;
imperfective = [-sima+nngit]; [-vallia-]; [-galak-]; [-a-] (as in tusaajuq "he is hearing"); etc.
*the pronominal endings in Inuit Languages may be classified as "unmarked/simple" perfective aspects (in some linguistic analyses this is known as "aorist" tense)...another important implicit proviso here as well is that verb quality may and do take on both tense and aspect (ie, present pronominal endings in Inuktitut have both tense (default "present" when not specified otherwise) and aspect (the selfsame default "perfective" when not specified otherwise) at the same time and in the same morpheme).
I remember once in a conference someone saying in disbelief that a non-English language may have a future-perfective, and I pointed out "will have had", so even trained linguists have a hard time grasping the full richness of this grammatical verb quality. Kant's notion of space-time itself is often read as only having to do with philosophical speculation (and I suspect even Kant didn't really appreciate the primitive linguistic reality of his profound insight and emphasized the cognitive aspects of it ad nauseam).
The Inuit Languages are rich in this "grammatical tense" function (no matter how they're analysed they only begin to make better sense when one recognizes them as such). This field is largely a virgin territory in terms of linguistic analysis, which is surprising in a way because - as shown in any conscious search of philosophical discourse - it has a deep and varied history in philosophy/scientific thought (ie, Kant wasn't the first and neither is he the last by any stretch of the imagination).