[lucius_verus]

Very few people use the recommended amount of sunscreen (it's more than you think) and even when you do, no sunscreen blocks 100% of the photo-aging UV energy that hits your skin (note: still wear sunscreen - absorbing 5 or 10% is better than 100% of the radiation you would otherwise absorb). This also means that (contrary to what weird sunscreen-truthers will tell you) wearing sufficient sunscreen does not prevent you from producing vitamin D - sunscreen is not the same as never seeing the sun.

[slothtrop]

Well by extension, you're still exposed to diffuse UV indirectly if you get natural light.