Erstwhile and Until now

Erstwhile adverb - At an earlier or previous time.

Until now and erstwhile are semantically related In some cases you can use "Until now" instead an adverb "Erstwhile".

Until now adverb - Used in negative statement to describe a situation that has existed up to this point or up to the present time.

Erstwhile and until now are semantically related in earlier topic. Sometimes you can use "Erstwhile" instead an adverb phrase "Until now".