How it's calculated
birth year = reference year − age (366-day window)
age = age in whole years on the reference date. Someone aged exactly N was born in a window spanning the day after (reference − N − 1 yr) up to (reference − N yr), covering two possible birth years.
Common questions
Why is the result a range, not a single date?
An age does not pin down a birthday, so the calculator returns the window of dates that match the given age on the reference date.
What is SSA full retirement age?
The age at which you can claim full Social Security benefits. It is 67 for anyone born in 1960 or later.