Yes. I tend to go into a pretty substantial depression....oh, about this time of year... late winter to early spring and have hypomanic spells in late spring to maybe midsummer. This is the first year I've been on a med that's been working, so it'll be interesting to see what happens. Recently, I've been feeling a descent, but I'm not sure if it's the usual seasonal thing...or being unemployed and really really bored... or that I moved in with my BF and he keeps the room where we spend far and away the most time dark all the time. I think it may be all these factors, but must admit that light really does effect my mood, and the dark room thing is really starting to wear on me. BUT, next week we're moving into an apartment that will solve that problem! (And will be finally able to look for jobs, which getting out of the house and having something to do should help as well.)
Sorry to ramble, but that's all to say that, yes, seasons and light have a substantial effect on my mood. (Last year, I had a huge shift on the day the clocks went forward -- usually it's not quite that dramatically calendar specific, lol!)