Old Time Used To Be Meaning

(idiomatic, euphemistic) Ex-girlfriend or ex-boyfriend. Often used in songs.

Example: Roberta, lyrics by Leadbelly
  I thought I spied my old time used to be. And it was not nothing, honey, but the side of a tree.
Somebody Loan Me A Dime. lyrics by Boz Scaggs
  Somebody loan me a dime, I need to call my old time used to be.