Eating chicken that has been expired for 2 days or longer is perfectly okay as long as the chicken has been frozen properly the entire time.
The expiration date doesn't always mean that the chicken is no longer safe to eat and is just a general guideline as to the freshness of the chicken.
When chicken is frozen it can last for 6 months to a year and sometimes longer past the expiration date but it must remain frozen until you're ready to cook it.
Only put the chicken in the refrigerator a day or two before you're ready to cook it and never leave the chicken out on the counter to thaw because bacteria can grow on the chicken.
Chicken that has gone bad will have a slimy feeling to it and a bad smell too it that would make you vomit but as long as it doesn't have a slimy feeling or a bad smell to the chicken then it's safe to eat.