Ken, back to your original statement which is actually not correct. As you stated, you are currently 69 and born in 1950. That sum today and for most of the year is 2019, not 2020.
So the statement is only correct for people who have already had their birthday. If one is born on January 1, the statement is true for 365 days. For the person born on December 31 it is true for only one day.
Remember, Abe Lincoln cautioned that not everything on the internet can be believed. I saw that on Facebook.
It is true if you use your age on your birthday of that year. So using 70, for example, which i turn 70 in 2020, it works.
As it should, simple math