I just read 'Journal of the Two Sisters' · 2:58pm Apr 19th, 2015
And whoooo boy. There is so much good stuff as far as fodder for creating an Equestrian and pre-Equestrian timeline, as well as a timeline for Star Swirl, Celestia and Luna, and the three pony tribes. Looking over my fic, I don't think I've written myself into too much of a corner, now that I know these details. I think I'll just have to do some minor tweaking here and there to establish what age we're in when the Sirens were fillies, and how all the ponies were living (or not living) together.
If you're into the attempt of getting your timelines as straight as possible in your fic, 'TJOTTS' is a pretty informative read. I recommend it!
I was considering referencing it, but after skimming the highlights a few major issues made me put it aside. The whole 20 unicorns burning their magic out a day to raise the sun/moon just become too much and I threw out 99% of the idea. Just my 2 cents of course.
2996986 Haha. That part was sooo extra. Thankfully they got their powers back. But just to alleviate my wondering about what was going on before Celestia and Luna, I enjoyed the book. Especially since in my fic, the Sirens, at the beginning of their lives, are living in that gap during the change from the pre-Princess sisters, three tribes era to the establishment of Equestria. So, I gotta go back and change a few things. But I think I've already done a pretty good job at keeping the three races distinct and mostly separated thus far. Idunno. We'll see.