Simple, lightweight and it works, just what you need for something like this.

Working as intended, big big thanks Simonkhzhang

Totally awesome this addon! Match perfectly with Win 10 1909 light/dark mode

YESSSS!! I've been many days thinking about how could I manage to achieve something like this, setting my two custom themes instead of using the default dynamic theme which I don't really like, and finally found it! Thanks a lot Simon for your idea and your time invested on this!!

btw, the themes I use and I totally love are:
Day: "Google Chrome Light" https://addons.mozilla.org/es/firefox/addon/google-chrome-light/
Night: "Google Chrome Dark" https://addons.mozilla.org/es/firefox/addon/google-chrome-dark/

Both made by the same user, StyleFox

是否可以加一个根据系统自动主题的选项？不喜欢用火狐的默认主题，因为标题栏是黑色的，非常感谢。

Best plugin to meet my need

Automatic sunrise/sunset times. JUST AMAZING

Not work on 66.0.3 and If you delete cookies addon was reset... Thanks for your effort. Working good now. :-)

don't auto with system df

Cool idea. A nice way to add variety, and a nice way to remind myself it's nighttime :-)

Finally I don't need to change my theme twice time a day

does exactly what it should and I love it

Nice addon!

I needed this in my life. Thank you <3

Works great, does exactly what it says it does.

I love it.It's working well.I can change the theme to anything I want.Thank you for this amazing addon