i was looking for something could make g calendar black and finally i found it! i would suggest to add "google calendar dark theme" as tag so it could be easier to find out!

terrible

Great Addon for webpages that don't support the dark mode.
I use the Addon with default off and turn it on for specific websites

Finde endkrass dieses Extension!! 👍👍👍👍

Exceptionally useful and very well made indeed. I see some reviewers say it slows down Firefox but I haven't noticed any decrease in performance.