However, this doesn't make sense to me because I personally know some brilliant people are morning type: maybe wake up at 4am or even 3am.
HN people, do you sleep late? Do you feel you have a higher IQ?
I don't remember ever taking an IQ test... but my personal anecdatum is that I feel more productive when I have a regular sleep cycle, but that can involve waking up at 7am or 9am or earlier or later and what that depends on, beyond the seasons, I don't know.
That being said I am an odd mix of morning person, night person. I function very well if I am out of bed by 6-6:30am, then I drop off about 11:00am. From 7pm-1am I again function at a high level. I typically only sleep about 4-5 hours per night and feel very groggy if I sleep more than that.
I agree with most of the other responses. I think your peak production period depends on the season, type of work and lifestyle.
For me, it also depends on where I am. In the city - get up late, go to bed late. In the village/farm house - get up 5:00-6:00 morning, go to bed earlier, usually 21:00-22:00.