I'm going for a similar visualization with my "year-in-pixels" project aimed primarily at spotting trends in mood and/or health symptoms, but I wanted it to be adaptable. Hence the name: https://howsyourblank.com
That actually looks really cool and mature. Since when have you been working on it?
What technology did you use?
Seems good but I am constantly getting "Error saving to local storage. Can't read property setItem of null".
Mhh, that's unfortunate. Either you have cookies disabled or you're using a browser that doesn't support localStorage.
The app needs it because otherwise all is lost when you close the tab.