I wonder if there's a language where grammatical tense is not expressed by inflections on its verbs, but by inflecting some other part of speech?
English marks tense in seperate words such as Auxiliaries and expletive (dummy) 'do'. In a sentence, these stand, syntactically-speaking: above / serially-speaking: to the left, of a verb:
This does not help. / This has proved helpful. vs This did not help. / This had proved helpful.
Verb = same
Time ≠ same
In Wolof, a language spoken in Senegal, Gambia, and Mauritania, the verbs never change their form, it is the pronouns that have the tense. In Wolof there is I-which-is-now, I-that-will-be, I-that-was, and so on, each pronoun has the 5 Wolof tenses, each tense having 2 aspect variants, perfect and imperfect. In other words, you take a past tense pronoun and the unchangeable verb and you get a past tense verb phrase.