Whenever you leave the end dimension via end portal, the lighting of the overworld will break. It appears to be the same kind of lighting used in the end (dark, greenish, pale), and even with the sun out the world is oddly dark.

How to reproduce:
1. set the time to day
2. Set your spawn on the surface
3. Go to the end
4. Leave the end
5. Observe odd lighting in the overworld
6. Relog to fix the lighting issue.

Expected results:
The overworld should have its normal lighting, instead of this strange end light.

I will link to footage of this once i have some, until then, here's some pictures below
Picture 1. Normal over world lighting.
Picture 2. Broken lighting after leaving the end dimension.