I made Michele Foster's Fondant on April 1st and had lots left over. It's wrapped good and in a zip lock bag. I need to make a cake this weekend and would like to use it. The fondant still smells really good and tastes wonderful.

Is there a way to tell if fondant is past it's date?

Fondant doesnt really have a past date, ive noticed when its started to go bad (and this is after almost a year btw, it starts to break down ) Your fondant should be absolutely fine!