Every language has its different grammar rules for tenses.
In English, verbs express tenses. They are inflected with the suffixes (-ed, -ing, -s) to indicate time (present, future, past, etc). ASL has its own grammar rules for tenses in some similar ways and some different ways.
For example, in an English sentence, "she gave me a hug last year", the past tense for the verb "give" must be inflected to "gave". This could be considered redundant or tautological in ASL sense; however, it's not incorrect in English. In ASL (like some other spoken languages), the sign "LAST-YEAR" is already a past tense itself: LAST-YEAR SHE HUG ME.
In addition to the time signs, the use of space, movement, repetition, and non-manual signal in conjunction with signs (verbs, adverbs, nouns, etc.) are other signifiers in expressing a time measurement and progress.
The signer uses an imaginary time line as a time indicator to express a relative measurement of how recent/distant past or future is.
One of the time indicators is the timeline of the signer's body (space) as the baseline of the present time as the illustration above shows.