how do Isolate the YYYY in DDMMYYYYXXXXX in a 4923x2 matrix?

I have given a task to convert a file to csv I Matlab, that not the problem, in the file I have til convert is 4923x2 matrix. 1. column is Social secruity Number with DDMMYYYYXXXXX,. I the file I have to export, I have to add a column with year of birth only. how do I isolate YYYY in DDMMYYYYXXXXX in my excel dokument, so I create a new matrix with year of birth.

[Jan]

Please mention, if DDMMYYYYXXXXX is a string or a number. How are the data available? Can you post the relevant part of your code? Then creating an answer would require less guessing.