The Eukleia festival is the first of three festivals that occur between Henatan and Theoxenia. The festival is likely marriage/wedding-related and is connected to torch races and athletic competitions. Eukleia is linked to musical and theater events in other parts of Greece, which may have been reflected in the Delphic celebrations. Many other traditions and rituals related to marriage are associated with the epithet "Eukleia", emphasizing its connection with marital customs, and its special importance for young unmarried women.
All that is known for certain is that Eukleia is the first of 3 festivals between Henatan and Theoxenia$^{5}$. The date of the 16th has been chosen for modern astronomical reasons, as well as correlations in other traditions.
Lines D7-8: A series of three festivals of Artemis are mentioned here: Eukleia, Artamitia and Laphria (see again Rougemont, p. 59, with refs.). For Eukleia, a common epithet for the goddess, see possibly here CGRN 107 (Kalaureia), lines 1-10. Note however that the Laphria are not necessarily tied to Artemis: Laphrios is notably found as an epithet of Apollo, e.g. Str. 10.2.21 and IG IX.1² 149 (Kalydon). Given the chronological sequence of the list in these lines, these must have fallen after 9 Bysios, either in that month, or during the following month of Theoxenios (this corresponded roughly to Athenian Anthesterion-Elaphebolion).
– A Collection of Greek Ritual Norms (CGRN) – Two excerpts from the dossier of regulations of the Labyadai at Delphi $^{5}$
The maiden (Parthenos / Virgo) rises above the eastern mountains after dark, and there are dates where the moon coincides with the maiden. Potentially important because:
Note that this could more strongly support the festival being placed at the full moon in ancient times.
[Thebes]
{9.17.2} Before the temple of Artemis Eukleia is a lion made of stone, said to have been dedicated by Hēraklēs after he had conquered in the battle the Orkhomenians and their king, Erginos son of Klymenos.
Pausanias, Description of Greece 9. 17. 1 $^{47}$
The Delphic skyline over the temple of Apollon in Delphi 2024 The moon is aligned with Virgo, and Leo rises above. Note that this is only true of the present day sky. Image constructed using Stellarium & google maps
Plutarch mentions that in Boeotia, engaged couples would sacrifice at the altar of Artemis Eukleia in the agora.
In addition to the rituals and customs associated with Artemis Eukleia, there are correlations with other traditions and practices related to marriage and festivities. One such example comes from Kos, where the celebration of marriage is organized in the month of Petageitnyos. According to ancestral customs, the marriage ceremony takes place on the 18th day, preceded by a banquet and a distribution of offerings. There is also a mention of Heracles, who is said to have donated a lion statue to the temple of Artemis Eukleia in Kos. Note also that Eukleia is sometimes said to be the daughter of Herakles, and Pausanias mentions that Herakles is said to have donated a lion statue to the temple of Artemis Eukleia. Altars and images dedicated to Eukleia can be found in marketplaces, and prospective brides and grooms offer preliminary sacrifices to her.
If one of the descendants in the male line seems to the members of the cult to be lacking in [private means, when] he is about to celebrate [his marriage], let him organise the marriage in the [month] of (90) Petageitnyos, the banquet on the 16th, the distribution on the 17th, so that the sacrifice for Heracles is accomplished according to the ancestral customs, on the 18th, the assembly, and on the remaining days (95) the marriage is to be celebrated.
– Dossier of the familial cult of Diomedon on Kos $^{75}$