The most important day for you and your skin. Just as summer begins as the memorial holiday starts, people rush towards the sunshine after a long dark winter. At this time, the sunshine is the most intense and harmful. The purpose of this day is to educate people and to make them aware of the dangers of overexposure to UVA and UVB rays. These UV rays come from the sun, and from popular tanning booths. They are the primary cause of skin cancer.