I was looking to calculate if someone was under 27 years old; this can Be quite tricky but excel has just the function, =DATEDIF().
returns the number of years between NOW and date held in cell B3. (It handles all the year rounding and leap years so there’s no need to worry about rounding etc.
will return true (1) or false (0) depending on if the difference between the dates is greater than 25 years of not.
I used the www.cpearson,com site as my guide.