Both sunlight and sunshine mean "the light of the sun," but sunshine additionally means (1) "happiness" or "cheerfulness," (2) the "source of happiness or cheerfulness," and (3) the "shining of the sun." "Sunlight lasted only a few hours today." "He basked in the sunshine of his friend's affection." "Your smile is all the sunshine I need." "She lies in the sunshine for an hour every sunny day."
Dictionary of problem words and expressions. Harry Shaw. 1975.