Paper v4.9 (Dark Mode)
A simple, clean, flexible Hugo theme.
Hugo themes: https://themes.gohugo.io/hugo-paper/
Inside the folder of your Hugo site, run:
git clone https://github.com/nanxiaobei/hugo-paper themes/paper
Then change in
theme = "paper"
For more information read the official guide of Hugo.
It's automatic, according to the natural time of day and night.