No lol, it's strength of Ultraviolet rays between 0800 and 1600 during the first day of each month of the year. It holds generally true for any place close to the same longitude as New York City; however, one can also infer what times of day and during which months it is essential to wear sunscreen. Personally I wear sunscreen no matter what, because we no longer live in a natural environment (in reference to the entire flippin' planet) and natural defences are not enough. Also, I do not want to experience age-based discrimination.
*Well actually it is a uv^2 map, because the curve of the line is related to the curve and rotation of the Earth.