Dieses, also known as Winter Nights, All Hallows or "Samhain", is generally celebrated in late October. As with the Celtic Samhain, a central focus of rituals during this time is honoring one's ancestors and any other dead special to the worshipers (e.g., passed friends, ancient heroes, etc.).
The term Dieses relates to the Norse Disir, who are the collection of one's female ancestors going back to ancient times. The Disir are helpful spirits who try to guide the living (their descendants) to making wise choices while in Midgard (Earth, this realm).