noun
way in the past; two decades ago; about twenty years ago
Refers to a time roughly twenty years ago, or more loosely a generation ago. Often used in contrast with 一昔 (about ten years ago) and 三昔 (about thirty years ago).
See also: 一昔
二昔前は、スマートフォンなんてなかった。
Twenty years ago, there were no smartphones.
この町の風景は二昔とすっかり変わった。
The scenery of this town has completely changed from twenty years ago.
一昔 means about ten years ago, while 二昔 means about twenty years ago.
三昔 means about thirty years ago, extending the pattern further into the past.
Compound of 二 (ふた, 'two') and 昔 (むかし, 'past, old times'). The reading ふたむかし follows the native Japanese counting system.