formula needed to add a number of years to a date

**Maryjoefernandez** · 09-18-2013, 08:07 PM

I need a formula the will allow me to add years, in number form with decimals, to a birthdate and give me the date the person will turn that age. For example, cell A1 has a dte of birth in it, say July 1/1975 , cell B1 has 25.5 in it, I need the formula for C1 that will tell me, in date form, the day the person turned or turns 25.5

Thanks

**cheeze83** · 09-19-2013, 04:04 AM

I think to be the most accurate you might want to have in C1

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Then in D1

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For your example, this would return 23/12/2000 which is when they would turn 25.5

If you change it to 25 it should then return 1/7/2000. It has potential to be out by a day or so here and there due to leap years, hence the x 365.3 to try and take this into account

**cheeze83** · 09-19-2013, 04:07 AM

Actually, sorry - put this in C1 and do it all in one cell...

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It's still early in the morning for me.....

**6StringJazzer** · 09-19-2013, 07:41 AM

The SUM function works but is not necessary:

=B1*365.3+A1

Also note that when you are working with fractions of ages and dates, you have to take into account leap year, which cheeze83 has done by adding 0.3 to the number of days in a year (a more precise number would be 365.256363004).

Note that this adjustment is only correct with regard to the calendar when your span is exactly 4 years, otherwise the answer will be a fraction of a day larger than the calendar. This is probably fine depending on your purpose, especially since you are not giving the exact time of a person's birth; just using the day for the birthday will use 00:00 of that day.