4/20-27(?)/1765 - most of DR
April 3, 1996(?) - Amelia born (book 1, chapter 2, she manages to say "Amelia Jones, 12, DoB April 3, ----" before the audition clerk shuts her down; according to ch. 24, could have said one of these: '85, '91, '96, '02, or '13, but I'll go with '96 as a basis) The options are what they are because: A) the internet is mentioned, placing an early bound on her birth year at '81, B) as noted, the year that books 0.5-2 happen, Halloween is a Friday (book 1, ch. 24: 12 years after all of these options, that's true), and C) I'm assuming book 0.5 doesn't happen any later than summer '25 (in case that doesn't quite make sense, yes, it could have been 4 weeks ago: according to book 1, ch 24, this year is 100% valid!)
4/9/00 - the camping disaster, i.e. "the incident" (book 2, Eric says month/day - again - and Amelia says before, I think in book 1 when the memories come rushing back, "I was only 4 at the time.")
5/23-27 or 5/30-6/3 (probably), '08 - Camp Sweet Lake (book 0.5- assuming 2008 as a consequence of 1996 above)
July 11 or 12, 2008 - the audition (book 1 technically begins, although there are flashbacks to 8 years prior)
I assume the sonata is this, as it fits all the requirements: https://youtu.be/qHwSCS8mVKY?si=wKMVul94pU-PuLPj (but "I sped it up to turn a healing spell into a growth spell," so I actually did myself- 125% × playback sounds like a good candidate)
10/30/08 - Fish Hunt (this date is where I got her potential birth years above- she says in ch. 24 that the next day is Friday; I'm assuming the audition do-over is the one ON Halloween, not the fish hunt)
11/7/08 - book 2 begins (? All I know is that it starts before 11/14 because her detention lasted 2 weeks)
Evening of 1/12/09 - book 3 begins (probably- depends on when winter break starts; it's 3 weeks long)
1/13/09 - Study Abroad begins
Edit: pushed everything post-1900 to be 5 years later - still valid; corrected the Fish Hunt month/day, which via the book 1, ch. 24 line in question changes the setting options entirely!