The New England Journal of Medicine published a case report of this 69 year old man who spent 28 years driving a delivery truck without wearing sunscreen. The left side of his face received more sun via the driver's side window-- and the differences are dramatic. The side of his face that saw more sun exposure is thickened, cobblestoned, rough, scaly, irregular, and lined. The right side of his face, which was relatively shielded from the sun, looks decades younger.
This man's face is its own case-controlled study about the power of sun in causing skin damage. To keep your face looking more like the smooth side, try to avoid spending time outdoors between 10am and 2pm. Wear long-sleeved clothing and wide-brimmed hats when you are at the beach. And always wear sunscreen (with zinc and titanium).