hitherto vs until now

hitherto and until now both are adverbs.

Word	Noun	Adjective	Verb	Adverb
hitherto	No	No	No	Yes
until now	No	No	No	Yes

As adverbs, hitherto and until now are synonyms defined as:

hitherto and until now: used in negative statement to describe a situation that has existed up to this point or up to the present time

Other synonyms of hitherto include as yet, heretofore, so far, thus far, til now, up to now, yet.

hitherto (adverb)	until now (adverb)
used in negative statement to describe a situation that has existed up to this point or up to the present time	used in negative statement to describe a situation that has existed up to this point or up to the present time