September 28 is the observance of the feast day to the goddess Zisa.
Zisa is seen as the founder and protector of the city of Augsburg in modern Bavaria. Augsburg was known earlier as Zizarim. Fraa Zisa was reported under various names (including Isis due to language confusion, apparently). She was particularly associated with the Suevi, who are the predecessors of the Swabians. The Suevi also mixed with the Alemanni and other tribes. There are quite a few locations in southern Germany and Switzerland named for Her. The tribes who knew Her were large contributors to the Pennsylvania German nation.
In the first century BCE, the Romans under Titus Annius laid siege to Zizarim just before Her feast day. Unfortunately for the Romans, many Swabian warriors were coming to Zizarim for the festival, and on Her day they attacked the Romans and throttled them.
Granted, the Romans years later did take the city, but the battle for Zizarim was a famous loss for Rome.
Zisa in the Christian era was depicted as the Virgin Mary with the extra appellation of "Undoer-of-Knots," which is drawn from the lore of the Heathen past. Images of Her from later centuries indicate that she has the ability to undo Urleeg if one's cause is just. Images of Her in this role have been restored in Augsburg's city hall.
She was so widely revered among the Suevi that their dialects called Tuesday "Zistag" not after Ziu but after Her. The Diocese of Augsburg banned the name Zistag and called it "Aftermontag" (After-Monday).
There are quite a few places that bear Her name as the root of their modern names. The church of St. Peter am Perlach stands on the grounds of Her temple at Zisenberg in Augsburg.
Her symbol is the pine cone and appears in Augsburg even in some churches. As the pine cone protects the seeds, so does she protect Her people. The pine cone symbolizes protection, regeneration, and continuity. Even though Augsburg was eventually conquered by the Romans, the Volk's relationship to Zisa continued, in symbolic form if not conscious form, into the present day.
In Urglaawe, Zisa is the consort to Ziu (Tyr) and is known to remove obstacles and undo knots for just causes. She is honored on Zisadaag (28. Scheiding/September).
Grimm, Jacob, James Stallybrass, Teutonic Mythology, volume I, pp. 291-299. New York: Dover Publications, 1966.
Pennick, Nigel. "The Goddess Zisa." Tyr: Myth - Culture -Tradition, Volume 1, pp. 107-110. Atlanta: Ultra, 2002.
Schreiwer, Robert L. and Ammerili Eckhart. A Dictionary of Urglaawe Terminology, pp. 72-74. Lulu.com, 2012. ISBN: 978-1-105-51712-9.