Ooh, other people in this space - I remember seeing Timeliner a while ago while researching UIs for the backend I had built before starting on my own frontend [0]. Chronomize looks interesting (I used the macOS calendar for a while before outgrowing it, but still mostly maintain compatibility), but I'm curious how you'll handle certain UI things (like showing financial transactions, which generally have a date but not a time, or things like photo albums where I could mark off that an album existed but not link to any images within it).
[0] https://tylerfreedman.com/hindsight