Today’s topic is the festivals and other holy days in connection to Poseidon.
Poseidon was honoured monthly at Athens on the eighth day of the lunar month, together with his son Theseus. This is a pretty easy thing to adopt doing in our times, though one should take care, the lunar month starts on the night following the first sighting of the waxing crescent of the Moon after her dark phase. It does not start on the New Moon as it is called today and defined astronomically, as that takes place during the dark phase of the Moon. Which is rather confusing, for how can the Moon be new if it isn’t there?
Anyways, another major Athenian celebration of Poseidon is the Poseideia festival in the month Poseideon (November-December). While its exact date is unsure, many celebrate it in conjunction with the monthly worship of Poseidon on the eighth day, as this happened in antiquity with some other festivals as well, taking place on the same day as a monthly celebration of the same Deity. It takes place around the same time as the Haloa festival for Demeter and Dionysos and pertains to Poseidon’s agricultural aspects. It serves to beseech Poseidon to let the rain, which is plentiful in Hellenic winters, seep into the soil to nourish the seeds of the crops and refill the water table that was lowered over the course of summer. But also to avert too much rain, which would cause floods.
The Isthmia at the Isthmos of Korinthos is one of the Panhellenic Games, dedicated to Poseidon Isthmios, instituted by Theseus according to legend. This festival would entail several agones, similar to the Olympic Games. These consisted of chariot races – very apt since Poseidon is the creator of horses -, wrestling, boxing, and pankration. these disciplines were open to men only. There were also poetic and musical contests which were open to women participants. These Games took place every other year, in the second and third year of the Olympiad cycle. Scholars have found a starting date of 582 BCE to me the most likely, though this contradicts mythical origins of the festival. Like the Olympic Games, a Sacred Truce was declared by Korinthos, to allow athletes safe passage to participate in the Games. Even at times when Korinthos was at war with Athens, the Athenians were still invited to partake in the Games (this occurred, for example, in 412 BCE). The Isthmian Games lasted until Theodosius I forbade them as pagan worship.
In previous posts, I also mentioned the Taureia festival in Ephesos, though I know nothing further about it. Similarly, Thessaly likely had a festival associated with the worship of Poseidon Petraios.
I know of no other festivals.