Adverbs of time tell us when an action happened, but also for how long, and how often. Adverbs of time are invariable.
Adverbs that tell us when
Adverbs that tell us when are usually placed at the end of the sentence.
• I saw Sally today.
• I will call you later.
• Later Robert ate some porridge. (the time is important)
Adverbs that tell us for how long
Adverbs that tell us for how long are also usually placed at the end of the sentence.
• My mother lived in France for a year.
• I have been going to this school since 1996.
For is always followed by an expression of duration, while since is always followed by an expression of a point in time.
Adverbs that tell us how often
Adverbs that tell us how often express the frequency of an action. They are usually placed before the main verb but after auxiliary verbs (such as be, have, may, & must). The only exception is when the main verb is "to be", in which case the adverb goes after the main verb.
• I often eat vegetarian food.
• He never drinks milk.
• I am seldom late.
• Generally, I don't like spicy foods.