This app's main purpose is to count when the sun's position that gives us vitamin D3 from its UV-B light at our current location (location permission needed). UV-B light from the sun is reaching the earth's surface on a certain degree elevation at minimum. If the elevation is too low, then there is no UV-B light at all, so no vitamin D3 for us.

Warning: Do not get too long under the sun without any protection (shade, clothing, or sunscreen/sunblock), the risk for skin cancer is higher when you are exposed to the sun for a long time without any protection.