at the same time vs notwithstanding

at the same time and notwithstanding both are adverbs.

Word	Noun	Adjective	Verb	Adverb
at the same time	No	No	No	Yes
notwithstanding	No	No	No	Yes

As adverbs, at the same time and notwithstanding are synonyms defined as:

at the same time and notwithstanding: despite anything to the contrary (usually preceding a concession)

Other synonyms of at the same time include all the same, even so, however, nevertheless, nonetheless, still, withal, yet.

at the same time (adverb)	notwithstanding (adverb)
at the same instant	despite anything to the contrary (usually preceding a concession)
overlapping in duration
despite anything to the contrary (usually preceding a concession)