I have experienced the mood shifting all day long, but it's rare for me. Usually I'm depressed all day long for months or hypo/manic all day long for months. According to my p-doc, since I went from severe depression from winter '08-'09 then suddenly switched to mania in Aug '09 and then back to depression in Oct '09, this is all one episode that is "mixed." I think of it as 3 episodes in one year, but you have to have a couple of months symptom free, I believe, for a shift to be considered a new episode. I think that's strange, but that's how the DSM-IV-TR classifies it.

Although I have depression all day for quite some time, I do have varying energy levels throughout the day that make things seem less or more bleak. Either I have energy until noon or one and then am deflated until late in the evening or I have no energy until about 4 at night and am good until bedtime. My evenings are almost always better than the day. I think that's typical with bipolar.