How to set up Formula to determine my aged in a given Year

maybe:
=INT(YEARFRAC( [date of birth] , [date of year in question] )
this will uses references to a cell with your date of birth and a cell with a date you want to know. It will account for what day in that year you want to know. So if your DOB is 12/12/2000 then any day before 12/12 will be 1 less than any day >=12/12. To only account for the year then set the day to be 1/1 for that year. For example:
=INT(YEARFRAC( [date of birth] , DATE( [year], 1,1 ) )
or in this case simply
= [year] - YEAR( [date of birth] )