How long would you have to be in the sun...?

How long would you have to be in the sun for it to damage the collagen? I just really don't believe this whole the sun ages you thing. You'd have to sun bathe for a very long time, the majority of people just hear this stuff randomly and believe it, with no context or research. With most things I'd think you'd need to be in the sun for a very long time, with the sun right in your face and most of the UV rays are blocked by the ozone layer anyway.