When my body is completely free to self-regulate its internal clock, my mind is most alert and I have the most energy between midnight and five AM. I had a "day gig" where I was e-mailed a set of tasks (internet research and some writing, mostly) and deadlines but rarely (if ever) anything vital within a 4-5 hour time frame and certainly nothing due by noon that couldn't be delivered six hours early. I was pretty much on the opposite side of the clock from my employers, but since nothing was ever late, it was never an issue.
I currently work in a bar where my shifts begin at 10:00 PM and end when the lights come on (2:00 or 3:00 AM, depending on the night). People who know me know better than to attempt to contact me before 3:00 PM; if I'm awake I'm a spacey, evil bitch (and occasionally I'm still in bed). Besides, you'd have to knock on my window because my phone is muted until 3:00 or 4:00.
The worst time I ever had as an adult was working a job that required I be there by 6:15 AM: I literally spent the entire day in a coma of brain-fog and nasty retorts. FWIW, I also lost ten pounds, because my feeding cycle wouldn't accomplish the switch, and we won't even
begin to discuss my "digestive issues"

. That job lasted four of the most painful months of my life, and it took almost a year before I felt "right" again.
Anyone who chirps about noon "not being early" simply doesn't understand that it's the middle of my sleep cycle: plain and simple.