Is it safe to use Stonewall Kitchen strawberry or blueberry jam with an "enjoy by" date of August 2013?

Generally speaking, the "enjoy by" dates are kind of nonsense for certain items (for some items it really does matter) and jam is one of them. Legally, companies have to put a date on their products and there is very little guidance with regards to how the time frame is determined. For example, a bottle of water has an expiration date of about 4-5 years after bottling, it's a arbitrary number. If it was sealed and stored in a cool dry place I'd say it is fine. You can call the company as Susan suggested, but they will likely tell you that you can enjoy "at your own risk" as they don't want to be held responsible if you do get sick. If the jar is open however, I'd toss it. Even in the fridge, all kinds of bacteria can grow.

I would contact the company rather than rely on opinions from here. There's usually a website address or phone number on the jar.