Every language has its different grammatical rules for time tenses. The verb words in English are inflected with the suffixes (-ed, -ing, -s) to indicate time (present, future, past, etc). ASL has its own grammatical rules for time tenses in different ways
In an English sentence, "she gave me a hug last year", the past tense for "give" has to be "gave". It can be considered as 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.
The signer uses an imaginary time line as a time indicator to express a relative measurement of how recent/distant past or future is. Space, movement, repetition, and facial grammar are common signifiers in expressing a time measurement.
If there is no past or future tenses mentioned in a ASL sentence, it may indicate the present tense. The present tense is used when the action is general and the action happens all the time in general.
The following ASL words are the examples of indicating the present time or in general: "tend-to", "always", "every-day", etc.
The structure for positive sentences in English in the past tense is: subject + main verb (past). For negative sentences, it is: subject + auxiliary verb (did) + not + main verb (base). She hugged me.
In ASL, the terms for the past tense are PAST and PAST+ (see the image), YESTERDAY, LONG-PAST, LAST-YEAR, etc. These show the space beyond the shoulder into the past.
Off the point: These glosses in capital letters mean glosses, not translation. I've seen students mouthing "PAST" when signing. It's not "past" in English. Ignore the glosses that are not suitable for translation. Glosses are for the sake of writing down notes. The glosses only represent the signs. The sign PAST can mean "in the past" or even "before" in English translation. But, there are two different concepts of "before" thus two different ASL words (signs). So how do you write down a gloss for "before". That's why we use PAST for that particualr ASL sign even when it is equivalent to "before" as in "I've seen the movie before", not as in "I need to see you before you leave." Think ASL when speaking ASL, not thinking English words when speaking ASL words. ASL is not words nor English. It's a language.
Some ASL terms for the future tense are: WILL, TOMORROW, NEXT-WEEK, FROM-NOW-ON, NEXT-YEAR, and so on.
The sign-word WILL (left) shows a regular or standard movement forward from the boundary line of shoulder.
On the other hand in the ASL word FUTURE (right), the signer can modify the length of movement to describe a distance of future. The mouth morpheme AAH indicates a distant future. Wiggling fingers also indicates a very distant future along with mouthing AAH.
The continuous tense is also known as progressive tense. The structure of the present continous tense in English is: subject + auxiliar verb (am, are, is) + main verb (base + ing). In ASL, the present continuous tense is indicated in contexts of conversation, when the action is happening, using NOW, RIGHT-NOW, STILL, and such.
The structure of the present perfect tense in English is: subject + auxiliary verb (have, has) + main verb (past participle). She has hugged me. The common ASL terms to indicate the present perfect tense are, in glosses,: FINISH/ALREADY, ALWAYS, SINCE.
"I've wanted to visit Japan for years." ASL: IX-me ALWAYS WANT++(modulated verb) VISIT JAPAN (SINCE MANY YEAR).
The structure for the present perfect continuous tense in English is: subject + auxiliary verb (have, has) + auxiliary verb (been) + main verb (base + ing). English: She has been hugging me.
In ASL, temporal aspects are used to modulate the verbs. Some common ASL continuous forms are: ALL-DAY, SINCE, etc. along with modulated verbs. This requires a separate post on this subject.
Related tutorial: How to tell future time.
Introducing tenses in ASL.