Here is a great post about Kemetic Calendars by Bastemhet:
Another good post about Kemetic Calendars from Making Bright:
The Big Fancy Kemetic Calendar Post.
I’m working on a Festival Calendar for Aset/Isis specifically. I’m including Kemetic (Ancient Egyptian) and Greek/Roman festivals for Her here.
Here are the sources I have used so far:
Temple Festival Calendars by Sherif El-Sabban
Ancient Egyptian Magic by Bob Brier (for the Cairo Calendar)
The Calendars of Ancient Egypt by Richard Parker
Cauville, Sylvie. Le Temple de Dendara: Traduction XV. Peeters, 2012.
J. Gwyn Griffiths, Apuleius of Madaurus: The Isis-Book: (Metamorphoses, Book XI). Brill, 1975.
Isis in the Ancient World by R. E. Witt
The Cult of Isis in the Roman Empire by Malcolm Drew Donalson
The Histories by Herodotus
Description of Greece: Volume IV: Books 8.22-10 by Pausanias
Feasts of Light by Normandi Ellis