Hi, Cora,
jumping in here, have you seen the book The UV Advantage, by Dr. Michael
Holick? It is a small volume filled with great info, and in the back
is a chart which gives the safe times of day to sunbathe by
skin type, latitude and season. Excellent book highly recommend it.
Dr. Holick conducted the definitive study proving the benefits of
Vit. D and sunshine on Breast Cancer patients.