Created a summary of Gloranthan Holy Days from all the sources that I have at hand. Used the most recent holy days found in the Cults of Runequest books (Lightbringers, Earth Goddesses, Lunar Way and Gods of Fire and Sky) and many others elsewhere. This means about 178 cults and brotherhoods. Some of the information comes from campaign specific sources and that has been mentioned at the end of the document. Some cults have random days as holy days and that has also been mentioned. This is not official material but tries to have as accurate information as possible.
Here is the link to the pdf.
Notes From Pavis 