In the last few snapshots, lighting has been completely broken. In the nighttime, the light level is still 15, meaning mobs won't always spawn, and mushrooms and other things cannot grow.
In addition, light levels do not automatically change, and a almost fully sealed box that was exposed to one nighttime will have full brightness.
Linked issues
Comments 2
The behavior appears to be the same to me as it has been for a very long time. The "sky" value remains at 15, and the "block" value changes. This is a duplicate of MC-10410, which is Works As Intended.
Please write information about your system in "environment", not where you are on Minecraft. 🙂