Back when and Erstwhile

Erstwhile and back when are semantically related. in earlier topic. In some cases you can use "Erstwhile" instead the phrase "Back when" as an adjective or an adverb, when it comes to topics like olden, in the past, previously in time or order.

Erstwhile adverb - At an earlier or previous time.

Back when and erstwhile are semantically related. Sometimes you can use "Back when" instead the word "Erstwhile" as an adverb or an adjective.