20年代にじゅうねんだいMeanings1nounthe '20s; the twentiesRefers to the decade of a century, e.g., the 1920s or 2020s. The century is usually clear from context.20年ねん代だいのファッションが再ふたたび流りゅう行こうしている。Fashion from the '20s is back in style.彼かれは20年ねん代だい生うまれだ。He was born in the twenties.