Ὀγδόη Ἱσταμένου, VIII day
From today's sunset: eighth day of Pyanepsion.
Theseia, in honor of the Hero: solemn procession, sacrifices and common banquet of the whole population, agones.
Sacrifice to the Amazons.
Kybernesia.
"That the war (against the Amazons) ended in a solemn treaty is attested not only by the naming of the place adjoining the Theseum, which is called Horcomosium (from the oaths of ratification) but also by the sacrifice which, in ancient times, was offered to the Amazons before the festival of Theseus."
Plut. Thes. 27.5
"The chief sacrifice which the Athenians make in his honor (Theseus) comes on the eighth day of the month Pyanepsion, the day on which he came back from Crete with the youths. But they honor him also on the eighth day of the other months, either because he came to Athens in the first place, from Troezen, on the eighth day of the month Hecatombaion, as Diodorus the Topographer states, or because they consider this number more appropriate for him than any other since he was said to be a son of Poseidon."
Plut. Thes. 36.3
"Philochorus says that Theseus got from Skiros of Salamis Nausithous for his pilot, and Phaeax for his look-out man, the Athenians at that time not yet being addicted to the sea, and that Skiros did him this favour because one of the chosen youths, Menesthes, was his daughter's son. And there is evidence for this in the memorial chapels for Nausithous and Phaeax which Theseus built at Phalerum near the temple of Skiros, and they say that the festival of the Kybernesia, or Pilot's Festival, is celebrated in their honor."
Plut. Thes. 17
The eighth day is always sacred to Poseidon and Theseus.
"Poseidon Asphaleios stands for the ogdoad."
"The eighth and the ninth of the month that begins: these are the best days to accomplish the man's works: (Hesiod) praises the eighth and ninth plausibly as they carry perfection (syntelestikai) and therefore he has dedicated them to the human activities...one (the eight), by having a perfect dimension, the other (the nine), by deriving from a perfect number (the three), bring to accomplishment the works undertaken in them."
Schol. Erga, 772-773
(Votive relief honoring Theseus. The inscription identifies the figures as Theseus (on the left) and Sosippos (the figure in the centre), who dedicated the stele. Sosippos raises his hand in a sign of prayer, symbolically presenting his son to the beloved Athenian Hero...
From Attica, 400 BCE, now at the Louvre...)