How do you add 18 years to a date in Excel?

[Guest]

I'm trying to calculate the date of a person's 18th birthday using a formula
in Excel. For example, if the birthdate is January 1, 2000 the age of
majority is January 1, 2018. What formula can I enter to have Excel
calculate the date for me?

 

[Guest]

If your date is in cell A1 this formula will do it for you:

=DATE(YEAR(A1)+18,MONTH(A1),DAY(A1))

 

[Guest]

This may be the long way, however, it worked for me...try this formula:

=C3+(18*365+4)

C3 would be the cell where your birthdate is. I multiplied 18 years times
365 days and had to add 4 because leap year occurs 4 times in an 18 year
period.

 

[Guest]

If you want to avoid determining how many leap years are in the period you
could use:

=C3+(18*365+(round(18/4,0))

Dave

 

[Guest]

Thats an interseting one, if you start your calculation of 18 years in the
future from the year 2000, and if a leap year occurs in the year 2001, then
you would have an extra day for the years; 2001,2005,2009,2013,2017 so you
would have to add 5 extra days. But if the leap year occured in the year 2003
then you would add an extra day for the years; 2003,2007,2011,2015 so you
would only add 4 days. how could you determine where the leap year is?

I think the only way is to use Kevin B's method. As this uses the excel date
system which takes leap years into account.

 

[dennisdonelson]

Kevin Backman - way cool. I had a much more convoluted method, with multiple steps & conversions. You rock.