Adjusting for your actual references,
Formula in E12 is
=DATEDIF(C9,EDATE(C8,12*22),"y") - I get a result of 6
Start Date (C9) is 5 Sep 1975
Birth Date (C8) is 1 Jan 1960 (so 22nd birthday is 1 Jan 1982)
There are 6 years between 5 Sep 1975 and 1 Jan 1982 (76 77 78 79 80 81)