While the "sell-by" date on a package of raw chicken is primarily for the retailer's benefit, you can use it to predict when the chicken is no longer safe to eat. This is because the chicken is at its best quality before that date, and quickly loses its quality every day after, as bacteria starts to grow. If the chicken is past its sell-by date by two weeks or more, it is too old to use.
The Chicken Timeline
Stores use the chicken's sell-by date so they know when to pull it from the refrigerators, and you can use it to know when to throw it out. If you refrigerate your chicken, you can still safely cook and eat it within two of the sell-by date. If you plan on keeping it for longer, freeze it as soon as possible. When you freeze raw chicken, it can last nine months. To check for signs of spoilage in refrigerated chicken that has passed its sell-by date, open the package. Chicken starting to spoil has a rancid, foul smell and a slimy film developing on its surface. If you detect either of these signs, throw it away. Note that chicken can be unsafe to eat but have no smell or change in texture. If it is more than two days past its sell-by date, throw it out.