many's the time (that)
Something has happened or one has done something a lot of times before in the past. Many's the time that I've made mistakes, but I've always owned up to them and accepted the consequences. Be prepared—many's the time you'll fail or stumble when you start up a new business of your own, but if you keep working hard, it will eventually work out for you.
many (and many)'s the time
there have been many times. Many and many's the time I warned him not to go to the swimmin' hole by himself. Many's the time she's forgiven her husband.