I wanted to ask for your opinion regarding Chelsea and April of Coconuts Musume's date of "graduation". They had no graduation, but everywhere I read it says they left in January 2000. I found some old articles, and gathering that info and Lehua Sandbo's various interviews I come to think that htey probalby left before January 2000.
The deadline for the audition was November 22, 1999, and Lehua sent in her application after the deadline. She still got to go to the next set of auditions on November 28 with two other girls (from what I understand from the info). Is it safe to assume that on the second round of the audition on November 28, Chelsea and April was out of the group? SHould the date when they left be set as December 1, 1999 instead?
Probably nobody has looked into this as closely as you, so I'd say use your best judgment. Since it doesn't seem like Coconuts Musume had anything going on (releases, concerts) in November or December, it's kind of a Schrodinger's Cat thing where whether they were graduated or not made no difference on the outside until they were announced as gone for the H!P concerts in January. Maybe it would be correct enough to just say they left in late 1999, but it was only announced in early 2000.
If I could say somethiing, I think it is fine if you go with the date it was announced. There are lots of Eggs or Kenshuusei that might've been gone for a while before their departure was announced, but it's still the announcement date that is written down as their official departure on their pages (partly because there is not a good way to pinpoint their actual departure date).