How to calculate date of birth by total number of Years months days

Hello every one

i have some people birthdates

i calculated how old are they by years months days in a specific date ( 01/10/2020 )

now i want to revers it

i want to calculate date of birth by total number of Years months days in same date ( 01/10/2020 )

i wrote this formula

=DATE(YEAR($C$1)-D3,MONTH($C$1)-C3,DAY($C$1)-B3)

but it is not working to calculate right date of birth in all column

some of it is right the others is wrong i do not know why

excel sheet attached

thanks

Originally Posted by MarvinP

Hi Elloli,

Because you are off by a single day, I'd guess you are missing those leap years where February has 29 days instead of 28.
Read https://www.learntocalculate.com/how...%20leap%20year.
where the leap years are divisible by 4.

so what should i change here

=DATE(YEAR($C$1)-D3,MONTH($C$1)-C3,DAY($C$1)-B3)

to solve leap years problem

in cell B3, place this formula, then drag down to all other cells:

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