Lack of light in the winter can definitely make me depressed. Then again, the long days and heat in the summer usually make me a lot more irritable, and I sleep a lot worse so that can easily lead to mood swings as well. Plus, I have noisy neighbors who like to stay out in their yard until 4 in the morning in the summer, so I prefer the fall/winter because at least I don't have to deal with that. I guess my favorite is bright winter days, when there's enough daylight but it's not so hot and loud that I can't sleep.