Forgive my poor wording, this question is a bit hard for me to phrase. Essentially, I'm just wondering when and where the switch from "day is bright, night is dark" to "the next day starts when it's still dark out and includes the sunrise and sunset and then some" was made and for what reason.
EDIT: Basically, why does midnight signal a new day instead of sunrise and when did anyone decide that it should be like that?
hi.. just to clarify: are you asking why midnight divides one day from the next, or why we might call, say, 7am "morning" even in winter despite the sun being not yet risen?
Those two statements seem consistent with one another. I don't think we ever switched away from 'day is bright; night is dark'. That seems like a pretty uncontroversial statement. But a day can also start at midnight.