I think R&D Lab is the only map in KF3 that set in the daytime.

One thing I noticed in Killing Floor 3 is R&D Lab is the only map that set in daytime. If you look at the roof (there's a room that have a roof with hole) you can see the bright light is shining into the lab.

The other maps are set at the night. I think convoy map is set at dawn.