Oooooh I like this a lot! I had Claude Code make me something in python quickly after I looked at the original post because I also prefer viewing time horizontally. I had mine do each month on a line. Sorry, didn't bother to host as a page. Here's the HTML/CSS though https://gist.github.com/bronco21016/d2d188c402b8e70c7bc115f4...

I like your layout a lot though so I might adapt that and there is still probably room to add the month label at the beginning of each month.