This post has been marked by the post author as the answer.
I don't know about the possibility of a gradual change; but, there is now being tested in the beta version of 2018-06-15 a command SetSkyTo("name of sky folder"). e.g. "dark".
There is a new player in zone script to test it out. I have used it and works like a charm. However, you will need to do a little more scripting in order to be more realistic unless you want a drastic change on purpose. The name of the lua script is "plrinzonechangesky.lua". The code is very simple:
local test=0
function plrinzonechangesky_init(e)
end
function plrinzonechangesky_main(e)
if g_Entity[e]['plrinzone']==1 then
if test == 0 then
SetSkyTo("dark")
test=1;
end
end
end
Alienware Aurora R7 with SSD 256GB boot drive ( C: ) and a secondary drive ( D: ) that is 2TB
Intel(R) Core(TM) i7-8700 CPU @ 3.20GHz 3.19 with Intel Turbo-burst
Installed RAM 16.0 GB
64-bit operating system, x64-based processor
Windows 10 Home
NVIDIA GeForce GTX 1070 with 8192 MB GDDR5 and 8095 MB shared system memory
