Wiktionary
days of yore
n. (context idiomatic English) the past; bygone days (nostalgic)
Usage examples of "days of yore".
In those halcyon days of yore, BH, Before Humans, life was an idyllic pleasure.
That was where the royal dragons dwelt in days of yore, and a cavernous dwelling it was, with iron doors so wide that thirty knights could ride through them abreast.