What shelf-life information is on chicken packaging?

Packaged chicken may carry a "sell by" and/or "use by" date,  both of which are determined by the processor.  These dates refer to the quality of the product, not  safety. 
 
Assuming the chicken is purchased in a refrigerated state, it should be prepared within two days or stored in a freezer. If the chicken is purchased frozen, "sell by" and "use by" dates are meaningless. Frozen chicken stays safe indefinitely.
 
Sources:
USDA Fact Sheets "Focus On: Chicken"