Most perishable foods sold in the United States have a freshness date of some sort, as a guide for shoppers. They're generally described as "use-by," "sell-by" or "best before" dates, rather than expiration dates, because in most cases they don't directly address whether the food is safe to eat. Instead, they're intended to tell you how long the product retains its best quality. For example, if you have a steak that's past its date by a day or two, there's every chance you can still cook it and eat it.
Use Your Judgement
The fresh, red color of any steak will fade to brown over a period of days. That's a natural process, as iron-bearing liquids in the muscle oxidize in contact with the air, and doesn't indicate spoilage. Instead of judging by color, open the package and use your nose. Good beef will still smell clean and fresh, with perhaps a hint of sweetness. If the steak smells strong and funky or feels tacky and slimy to the touch, it's been colonized by spoilage bacteria and should be discarded. Unfortunately, this can happen even to steaks that are well within their freshness date, if they aren't kept cold.