I’d suggest removing the :focus outlines on the forward/back buttons when clicked. They sort of hinder the aesthetic, and as far as I’m aware if they’ve been clicked then there’s no chance you’re causing an accessibility issue.
Good job with this :)
edit: oh another thing I’d suggest is caching the ajax requests for prev/next months if possible. It makes things feel suuuuper snappy. Here’s one I built out, I start loading the adjacent months immediately and cache already-loaded months so if people want to toggle back/forth it’s quick.
PS I think the way you handled the year view is a lot more elegant/usable than what I was trying to implement, nice job :) Might be neat to have some sort of toggle between views.