Good call. I think sometimes we celebrated the setting of the sun (bringing on the time to feast, to escape the scorching heat, etc). And sometimes we mourned it (the cold night, dangerous lurking in the darkness, and so on). I think most religions formed out of fear of darkness and love of sunlight. We were intimately connected to the sun, moon, stars, and seasons for MILLIONS of years. Eventually, our culture and beliefs revolved around them. We're moving away from that nowadays, and starting to forget.