Always skylight level 15 during the night, no mobs will spawn, even on hard mode.

Always light level 15

What I expected to happen was...:
Normal light levels, mobs that spawn during the night.

What actually happened was...:
Even with no blocklight and at night, the light level is always 15. No hostile mobs spawn. 

Steps to Reproduce:
1. Put my PC on.

2. Openen Minecraft.

3. Loaded my world.

4. Done