Athenian Feasts

Each Greek polis had its own calendar, though they had similarities. All their calendars were lunisolar, which meant they had twelve lunar months (generally alternating 29 and 30 days), and an occasional 13th month to keep the year in time with the Sun (i.e. the seasons). Each month was divided into three ten day phases tied to the rising moon, the full moon and the waning moon.

At Athens, the twelve months of the festival calendar started at a new moon in Summer:

There was a second, political or "conciliar" year, which divided the year into 10 "prytanies" of 36/35 days (perhaps 39/38 in catch-up years). There was one "prytany" for each of the "phylai" (the Athenian tribes).

These are the principal feasts in Athens. (From: Bruit Zaidman L., and Schmidt Pantel P., Religion in the Ancient Greek City, trans. Cartledge, P., CambridgeUP, Cambridge, 1992, p.103).

Festival	Month and day	Divinity
Kronia (Harvest)	Hekatombaion 12	Kronos
Synoikia (Unification of Attica)	Hekatombaion 15-16	Athene
Panathenaia - greater and lesser (Contests, processions)	Hekatombaion 21-29 (?)	Athene
Eleusinia (Grain) and departure ceremony for Phaleron?	Metageitnion (?) [4 days]	Demeter
Niketeria (Victory)	Boedromion 2	Nike
Plataia (Reconciliation)	Boedromion 3	Hera (Daidala)
Genesia (The dead)	Boedromion 5	Gê
Artemis Agrotera (Birthday of Artemis the Huntress) later called Kharisteria (Thanksgiving)	Boedromion 6	Artemis
Demokratia (Democracy)	Boedromion 12	Zeus Agoraios, Athena Agoraias, Themis
Eleusinia (Greater Mysteries, procession to Eleusis)	Boedromion 15-17, 19-21	Demeter
Pyanopsia (bean-stewing and olive/laurel branch decoration)	Pyanopsion 7	Apollo
Theseia (Cimon and the bones of Theseus)	Pyanopsion 8	Theseus
Stenia (women insulting each other, "aiskhrologia" and piglets given to snakes)	Pyanopsion 9	Demeter
Thesmophoria (autumn sowing)	Pyanopsion 11-13	Demeter
Khalkeia (Bronzes - craftsmen)	Pyanopsion 30	Athene
Apatouria (registration of young men)	Pyanopsion (?)
Oskhophoria (young men and grape vines)	Pyanopsion (?)	Athene
	[Maimakterion]
Haloa (offering of fruit)	Poseideion 26	Demeter
Theogamia (the gods' marriage)	Gamelion 2	Hera
Anthesteria (flowers to herald the Spring)	Anthesterion 11-13	Dionysos
Diasia (bloodless Spring offerings)	Anthesterion 23	Zeus Meilichios, the Gracious
Asklepieia (athletic and drama festival)	Elaphebolion 8	Asklepios
City Dionysia (procession and theatre	Elaphebolion 10-14	Dionysos
Delphinia (maidens' procession)	Mounikhion 6	Apollo
Mounikhia (young girls "act the bear" at Brauron)	Mounikhion 16	Artemis
Olympieia (equestrian games)	Mounikhion 19	Zeus
Thargelia (first fruits offered and scapegoat expelled	Thargelion 6-7	Apollo
Bendideia (Thracian goddess, procession, torch race)	Thargelion 19	Bendis
Plynteria (temples closed and Athena's clothes washed	Thargelion 25	Athene
Arrhetophoria (girls and secret objects)	Skirophorion 3	Athene
Skira (procession from the Acropolis to Skiron)	Skirophorion 12	Demeter
Dipoleia/Bouphonia (Ox eating grain on altar)	Skirophorion 14	Zeus

Summer (June - September)	Hekatombion, Metageitnion, Boedromion
Autumn (September - December)	Pyanopsion, Maimakterion, Poseidon
The intercalendary month every 3 years	second Poseidon
Winter (December - March)	Gamelion, Anthesterion, Elaphebolion
Spring (March - June)	Mounikhion, Thargelion, and Skirophorion