Well, suppose you had a 1 year-old child now, assuming the tree was alive or, very recently dead, if you didn't mark or rememebr the year it was cut down, you would 'off' a few years when the the child needed a science fair project in 3rd grade or w'ever. So, if you cut a tree down tomorrow, just put a piece of masking tape on it with 'cut in 2020' or similar on it. Or, you already have one sitting around and you KNOW you cut in down 3 years ago, mark it 2017 before you forget.
then, when the child starts counting rings backwards , they would be 'in sync'. Might even be able to correlate wide or narrow rings with documented local flooding or drought records as a double check.
If your oak were dead, and you did not know for certain when it died, local records for drought years could help align the tree rings with calendar years.