Hi. I am helping our social worker in preparing a masterlist of beneficiaries for the govt amelioration assistance (Php5,500.00 or $100) to the vulnerable families (COVID19). The form requires us to separate the birth month ("0#"), birth date ("0#) and birth year in three columns. To fast track the encoding of the year, I formatted it as "19##" so only the last 2 digits are supplied. If the birth year of a beneficiary falls in year 20 not 19, I change the format to general.
After that we need to calculate the age so I joined the birthmonth date and year to get the full birthday in a helper column.


The formula =INT(YEARFRAC(Birthday,DATE(2020,3,31))) however returns the value of 5 as the age of a person whose birthday is 9/9/25.
The date (birthday) is formatted as dd/mm/yyyy.
How do I correct the formula?
Thank you.