Here are the Aset (Isis) festivals listed in this book: Bricault, Laurent. Les Cultes Isiaques Dans Le Monde Greco-romain (La Roue a Livres / Documents Book 66). (Les Belles Lettres, 2013), 376-378.
The festival of Aset Pharos (Isis Pharia) does not have a specific date attached to it besides the month of April. Some place it on the 21st of April while others place it on the 25th of April coinciding with the Sarapia (Festival of Sarapis).
The two Isia Festivals (October 28-31; November 1-3) have to do with Aset mourning the death of Wesir (October 28-31) and then rejoicing at finding Him (November 1-3). Isia is also a generic word meaning “Festival of Isis”.
March 5: Navigation of Aset/Isis
March 20: Festival of Peluse (Pelusia)
April 25: Festival of Aset (Isis Pharia)/Sacrum Phariae and Festival of Serapis (Serapia)
August 12: Festival of Lamps (Lychnapsia)
October 28-31: Festival of Aset (Isis)/Isia
November 1-3: Festival of Aset’s Rejoicing/Isia