before (one's) time
Predating one's tenure or when one was born. A: "Have you ever seen this show?" B: "No, sorry, it's before my time." I don't know how that project was organized—it was before my time.
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
*before someone's time
happening before someone was born or old enough to know what was going on. (*Typically: be ~; happen ~; occur ~.) Of course I don't remember it. It was before my time. All that happened before your time.
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs. © 2002 by The McGraw-Hill Companies, Inc.