Adverbs are a closed class. Adverbs can be used either as a verbal suffix or independently to describe the entire utterance. See Also: Adverbial Phrases
A subclass of adverb are the modals, words used to denote properties of sentences, such as their reality, probability or the speaker’s emotions towards the topic. These may only be used independently.
Some modals dealing with time are zero-derived from abstract nouns.
laru this year
tariti at noon
Numbers can be suffixed to denote other times.