I want to see the actual age of my prospects or customers

I want to see the actual age of my prospects or customers

How can I get to a list that shows the actual age of my customers?
Currently it shows in the way of 5/03/1945 I want to be able to separate the list show the age for example "64"..
So if I were to print off a list ..I can tell it that I want everybody who is 64 years old..
Or everybody who is 54..etc

or everybody's who wedding anniversary is 20 year anniversary