I think you may just be experiencing switching, or a mixed episode -- including switching from purely up to purely down, as well as experiencing both at the same time -- which can happen with ADs and bipolar. I'm not sure if it's ultra-rapid cycling you're experiencing.

That said, I'm on an AD but do not experience mood shifts throughout the day. I'll experience emotional swings based on my mood state, but my mood won't go from down to up in the same day.

Once I'm depressed, I stay there like a lead balloon and have to wait until it slowly lifts. Once I'm "up," I stay there for a while. And then I get back to the inevitable mixed state, which I seem to stay in the longest, but I'm not sure. It could just feel like the longest because it's the worst.

I haven't tracked for long enough to get a specific timing pattern down, and my whole climate seems to have changed after the past couple years, so I'm trying to grasp the pattern of things. I definitely don't cycle that rapidly though (if I am bipolar at all, which I don't even know, but I do suspect it).