You have a good point Al, I wear mostly t-shirts & shorts in the warmer weather. In all my years I never recall being sun burnt on any part of my body that was covered, only the bear skin got burnt.
I use to only burn early in the year if I wasn't careful but now it seems that I can get a burn even after I have been exposed to the sun for a while, guess it's that age thing and skin getting thinner. Time to cover up, just don't care for sun screen.