The span of a day is from sun rise to sun set !)
What is a day? Who defined it? Were they right? Or do we just believe them?
I remember reading in the Bible that a day to God is like some immeasurable amount of time to us.
Or something along those lines.
My point is ... what if ... in order to twist up our understanding of things ... they switched night and day.
We don't really know ... we just go along with what we're told a day is ... and believe it.
I think it's debatable, if one were inclined to do so, but most often we simply accept it as fact.
I suppose it's easier.