Hello,
I’m working on a day/night system. everything is working except the night. During the night, the lighting does an odd thing. First of all you have to know that when the sun angle reaches 0, so when night starts, the directional light intensity is set to 0 and the sky light intensity is set to 0.2. However, it does that odd lighting: it goes dark for a moment, then very bright at midnight, then dark again, and back to day. What the hell? I disabled ALL kinds of lighting !
Thanks in advance for the help 
How are you determining when the sun angle is 0?
I used this tutorial : A new, community-hosted Unreal Engine Wiki - Announcements - Unreal Engine Forums
I haven’t gotten into doing the moon using the starter content skybox, at least not yet. I figure there should be a way to replicate the code that puts the sun in the sky, but changing the visuals to a moon and inverting the location on the sphere relative to the sun.
There should things you can purchase from the marketplace if you’re able to spend money on the solution, otherwise I would do some searching on some wiki’s and YouTube as to creating a realistic day night cycle.
Here’s a 3 part playlist on day/night cycle stuff I’ve found. Part 3 goes into depth on making night time lighting look great. I hope its helpful.