What's with the dark side of the moon?
Usually I see real moon phases in minecraft. Half moon, Crescent moon, Full moon, ect.
Tonight, I see this.
What gives? An Eclipse isn't likely, as the moon is progressing through the sky WITH the darkside matching its pace, rather than going in the opposite direction.
Solution 1:
You could as well ask, "why is the moon square?"
Minecraft is simply not realistic; you can't expect it to be scientifically correct.
This is just a phase of the moon, called "new moon", made by the developers as accurately as they could or wanted to.