These are the days sacred to Aset within each month. These are not the yearly festivals, but monthly ones. Some were Egyptian in origin and belong on the lunar calendar and others were adopted from the Greeks or Romans living in Egypt.
Many of these festivals are governed by the cycles of the moon. Aset (Isis) is honored on these days along with either Her son Heru-sa-Aset or Her Husband Wesir as they are both moon gods. Aset Herself is more associated with the sun in Egyptian cosmology than the moon. Her association here has to do more with the cycles of Heru-sa-Aset (birth to death or injury and healing of the Eye of Heru) and Wesir (death and renewal).
1st Day of Each Lunar Month-Sacred to Aset
From the astronomical ceiling of Senmut, this day is being noted as being sacred to Aset.
3rd Day of Each Month-Birth of Aset
This festival is from this book Ahnas el Medineh: The Tomb of Paheri at El Kab. Aset’s birthdays were celebrated with the lighting of candles and feasts were made in Her honor. Today, you could offer Aset a Birthday cake (blue, white or chocolate seem to go over well) and cook a great feast.
4th Day of Each Month-Offering to Aset of Philae
Make offerings to Aset, the Goddess of Philae today. Possible offering ideas can be found here: Offerings.
6th Day of Each Month-Sixth-Day Feast
This feast was associated with honoring the ancestors as well as Ra and Wesir. Aset Herself was given an oblation on this day.
7th Day of Each Month-Seventh Day Feast
Listed within a hymn from the Temple of Philae, this festival was initially associated with Ra. You could honor Aset and Ra on this day.
8th Day of Each Lunar Month-Sacred to Aset
This is listed within the Frieze of the Temple of Edfu. I don’t have much more information on this besides that at the moment.
15th Day of Each Lunar Month-Goddess Fifteen
This is supposed to be the Full Moon.
22nd Day of Each Lunar Month-Festival of Sopdet
Aset can be honored here as Sopdet as the cycle of the star’s departing and returning can be celebrated monthly along with being celebrated yearly.
New Moon-Festival of the New Moon of Aset
This is listed on the Temple of Abydos and it mentions oxen are given to the Goddess. This may also be the First Day of the Lunar Month as that is normally on the New Moon.
David, Rosalie. A Guide to Religious Ritual at Abydos. Warminster: Aris and Phillips, 1981.
Donalson, Malcolm Drew. The Cult of Isis in the Roman Empire: Isis Invicta. (New York: Edwin Mellen Press, 2003), 82.
Griffith, F. Ll. Catalogue of the Demotic Graffiti of the Dodecaschoenus. Volume 1 Text. (Oxford University Press, 1937), 46.
Morgan, Mogg. The Wheel of the Year in Ancient Egypt. Mandrake of Oxford, 2011.
Naville, Édouard Henri and Francis Llewellyn Griffith, et al. Ahnas el Medineh: The Tomb of Paheri at El Kab. (Egyptian Exploration Fund, 1894) 28.
Parker, Richard. The Calendars of Ancient Egypt (The Oriental Institute of the University of Chicago. Studies in ancient oriental civilization). University of Chicago Press, 1950.
Zabkar, Louis V. Hymns to Isis in Her Temple at Philae. London: University Press of New England, 1988.