Nothing jumps out at me, but I did want to say just for the sake of mentioning it, something that I always had a tiny "aw" at was that Vanguard placed Ayelbourne's message ending the brief Federation-Klingon War on March
23rd, just one day after Kirk's birthday and the anniversary of the Xindi attack. That would've been some great parallelism if it'd been placed just one day earlier.
Of course, it also means that "Errand of Mercy" spans Kirk's birthday, which must've been fun for him.
Edit: Oh, right, I guess I do have one comment I just thought of: because Vanguard puts "Errand of Mercy" so near the end of the month, I put the entirety of EoV in March, since it doesn't seem to span too long a period of time; I've got the start of book 1 just about right at the beginning of March based on my attempt at day-counting that trilogy, and "Devil in the Dark" right near the end of February since it didn't seem to have been too long before the start of EoV book 1 based on how it was described. That's probably another "up to you" thing though, I don't remember if there's room for a long gap between book 2 and "Errand of Mercy" or not but there might be.
Edit2: Oh, I just noticed your note about placing long stories at their
end. "The First Peer" should definitely be moved later, then. It
starts a month after "The Deadly Years", but the story spans a good few
khaidoa, which (going by Christopher's calculations) are usually around 40-50 days apiece (though with a ton of variance
khaidoa to
khaidoa). I've got it spanning from September 2267 to February 2268 myself, but that's just a vague estimate. There is another datapoint that backs up both the September placement of its start and the August placement of "The Deadly Years", though, which is nice; chapter 3 makes reference to D'Tran's first meeting with Lujok from "Precipice" having just recently happened, which just happens to have occurred on September 12th 2267.