When kept frozen the chicken can last in the freezer for up to a 12 months which is a year and sometimes longer.
I've had frozen chicken at the bottom of my freezer for 3 years before and it was still good and safe to eat.
The freezer keeps the meat and chicken cold enough so that bacteria cannot grow on the chicken or any other meat.
The chicken or other meat will not be as fresh the longer it sits in the freezer but the chicken and any other meat will remain safe to eat as long as it's kept frozen.
My Grandma who died had 10 year old chicken in the freezer when she died and I took it home and thawed it out and smelled it and it was okay.
So as long as the chicken smells good it's okay.