Usually that's a "best by" date, not a true expiration date. It might say it expires by a certain date, but with modern packaging, and as much preservatives and what not in things these days, you are probably just fine. I would try a few while at home just to be sure though.
I take expired bars and other things with me every year. My work affords me the opportunity to build up a collection of snacks and other things throughout the year. I just put them in the freezer until I need them and have never had an issue. This year I will be bringing 2-3 year old probars, Justin's hazelnut butter that I know is atleast 3 years old, Bobo bars I've had for atleast 2 years, and jerky from ???
With the way the world is now, I think expiration dates is a thing just so companies can cover their ass. However, I'd you ask my wife about the milk expiration date, come midnight, it turns into the most toxic thing on earth.
I've made her pancakes with the same expired milk and it's never been a problem