much much easier way to do this (in my humble opinion). Cut and paste this formula into the default value of the control to store the age.
floor((number(substring(today(), 1, 4)) + number(substring(today(), 6, 2)) / 12 + number(substring(today(), 9, 2)) / 365.25) - (number(substring(@DOB, 1, 4)) + number(substring(@DOB, 6, 2)) / 12 + number(substring(@DOB, 9, 2)) / 365.25))
Change the @DOB to the field which contains the date of birth.