When looking above player in most times of day, there appears to be a darker area in sky:

Steps to reproduce:

1. Enter any world with Ray tracing turned on
2. Look at the middle of sky above yourself

Observed results:
There's a darker point in the middle of sky

Expected results:
Sky color on that point should follow how sky color gradient is

I edited an image for better understanding of how it should be:

Side notes while reproducing:
In sometimes of day you can't see it such as Noon
Best times to observe it are: (you can use /time set command)

• Day
• Sunset 
• Sunrise
• Night

In midnight or noon you can't or hardly can see it.