[Ger-Poland-Volhynia] Gregorian/Julian Calandar

[Marlo50]

I understand they changed colanders and why they did it but I am wondering why was our ancestor's birthday changed?  She was born on 22 September 1882 in Volhynia.  They came to USA in 1888.  She always said
she was born 4 October 1882.  Now I know that 11 days were eliminated from the calendar  but why was her birthday changed?  There is still a 22 September.
Not to appear dumb but I am confused.  Anyway Russia did not go to the Julian Calendar until 1918.
Can anyone give me a sensible explanation?
Thank you.
Marlo