My BF is a sales rep for Bell/Giro. He says the dates are on there because lots of products have production dates and it has nothing to do with a "use by" date or anything like that. The helmet companies recommend using a helmet for up to 3 years from the time of purchase (depending on how you treat it.) Apparently dropping it, throwing it in your car, etc. can take a toll on the foam.

So don't worry about how long that helmet has been on the shelf