What is the biological property of 3am to you? Is it a particular time of darkness? Is it a set point of time after you have woken up? What happens when you travel to a different time zone, do you adapt?
As I understand it, it's more of an internal clock that can be shifted by sunrise/sunset light/dark - but there appear to be a biological/inherited component. Hence some mammals have evolved a rhythm more dependent on seasons than day/night, due to polar day/night cycles:
https://www.researchgate.net/publication/41942188_A_Circadia...
Which in turn might imply that humans still being rather young species is tuned to a rather strict day/night cycle, as seen close to the equator.
