This mod is called AlwaysNoon, and it is a true "daytime" mod, making it always the middle of the day using only code.
The bootstrapper creates a client component, which uses Reflection to invoke the otherwise private method ClientRemote_ServerTimeOfDayOffsetUpdate which is in TimeOfDaySystem and pass a false serverTimeOfDayOffsetSeconds value, resulting in your client to believe that it is always the middle of the day.
Here is the source code: https://github.com/doug147/AlwaysNoon (https://github.com/doug147/AlwaysNoon)
Here is the download link: https://github.com/doug147/AlwaysNoon/releases/download/1.0.0/Noon.mpk (https://github.com/doug147/AlwaysNoon/releases/download/1.0.0/Noon.mpk)
Also here is a video demonstrating the outcome. The first part of the video is before I load the mod, the second part of the video is after I load the mod. It is a simple yet effective mod. If you think it is too bright all the time, you can adjust the values.
https://cdn.discordapp.com/attachments/743899164072476673/752285600673169438/CryoFall_2020-09-06_17-53-56.mp4 (https://cdn.discordapp.com/attachments/743899164072476673/752285600673169438/CryoFall_2020-09-06_17-53-56.mp4)
Before
(https://i.imgur.com/Q14TUk6.png)
After
(https://i.imgur.com/QEbXn1y.png)