When I played minecraft, I noticed that when I'm under trees or hills, sky become darker. Then darker the place, then more sky goes to black.
Added screenshots to show how it works. First in self-made tunnel, and second in hill. All screenshots was made on sunny day in normal world on the surface.
Duplicate of MC-31681, please use the search function to see if your bug has already been submitted. Currently over 47% of tickets are being resolved as duplicate.