On finding other timelines
I'm not sure how I missed this earlier, but while trying to tighten up parts of the timeline I came across this discussion on MyDramaList. It pulls together a lot of key dates and details, and it helped clear up a few things I wasn't fully sure about.
I ended up spending a while going through the thread. There are a lot of different posts and perspectives in there, and seeing how people worked through the details helped me sort out a few things I had wrong or hadn't fully pieced together.
A special thank you to MadelineMaureen for taking the time to compare notes with me and talk through some of the details. That back-and-forth was especially helpful.
And more generally, thank you to everyone who contributed there.
It genuinely helped make this timeline more accurate.