Ancient Greek calendars

Various ancient Greek calendars began in most states of ancient Greece between autumn and winter except for the Attic calendar, which began in summer.
The Greeks, as early as the time of Homer, appear to have been familiar with the division of the year into the twelve lunar months but no intercalary month Embolimos or day is then mentioned, with twelve months of 354 days. Independent of the division of a month into days, it was divided into periods according to the increase and decrease of the moon. Each of the city-states in ancient Greece had their own calendar that was based on the cycle of the moon, but also the various religious festivals that occurred throughout the year.
The Greeks attributed and dedicated each day of the month to a different entity, such as the seventh to Apollo. The month in which the year began, as well as the names of the months, differed among the states, and in some parts even no names existed for the months, as they were distinguished only numerically, as the first, second, third, fourth month, etc. Another way that scholars kept time was referred to as the Olympiad. This meant that the Olympic Games had just occurred and according to the four-year span, the games would not be held for another three years. Of primary importance for the reconstruction of the regional Greek calendars is the calendar of Delphi, because of the numerous documents found there recording the manumission of slaves, many of which are dated both in the Delphian and in a regional calendar.
It was not until the second century BCE that the ancient Greek calendars adopted a numerical system for naming months. It is theorized that this was more for uniformity across the regions than to secularize the calendar. The newly numerical calendars were also created in regions federated from the leagues of Phokis, Ozolian Locris, and Akhaia.
Below are fifteen regions of the ancient Greek world and the corresponding information of the yearly calendar.

Calendars by region

In the following tables the month names used in each Greek-speaking city are laid out with Athenian Greek letters transliterated into English letters, and with a leading ordinal number column. The ordinal column is mostly for reference, and should not be read too literally: Different cities started their calendar year at different points in the solar year, and the month-numbers do not reflect the start date, which for some cities is not known. Not all of the calendars are equally well-known, and confidence and uncertainties are discussed under individual headings, below. Calendars changed from time-to-time and from city-state to city-state on an irregular basis, sometimes for intercalation.

Aetolian

The months of the Aetolian calendar have been presented by Daux based on arguments by Nititsky based on synchronisms in manumission documents found at Delphi. The intercalary month was Dios, attested as Dios embolimos in SEG SVI 344, equivalent to Delphian Poitropoios ho deuteros. The month Boukatios corresponds to Delphian Daidaphorios, while Delphian Boukatios is Aetolian Panamos. There has been no argument to dispute the order of months, so the months found by scholars are agreed upon to be the most likely for the time. Unfortunately, there is no convenient table that describes the synchronisms, as one inscription is given for all the months. The only month to have a singular document describing it is the eleventh month, in comparison to the other numerous documents for the rest of the calendar. The Aetolian calendar was used across the League, and additionally, one could find the Aetolian calendar in use across western central Greece until the league dissolved circa the second century BCE.

1	Prokúklios	Προκύκλιος
2	Athanaíos	Ἀθαναίος
3	Boukátios	Βουκάτιος
4	Diós	Διός
5	Euthaíos	Ἑυθυαίος
6	Homolṓios	Ὁμολώιος
7	Hermaíos	Ἑρμαίος
8	Dionúsios	Διονύσιος
9	Agúeios	Ἀγύειος
10	Hippodrómios	Ἱπποδρόμιος
11	Laphraíos	Λαφραίος
12	Pánamos	Πάναμος

Argolian

Attic

The Attic calendar, otherwise known as the Athenian calendar, is one of the best known regions today. There are numerous articles that can detail what the months are named and how the calendar came to be attested. The Attic calendar consisted of twelve months and twenty-nine to thirty days, much like the calendar now. Occasionally, the Attic calendar would be thirteen months and have an intercalary year to keep the festivals aligned with the differing seasons. Additionally, the Attic calendar created extra days to have the festivals align with the lunar cycle.

Festival calendar

With the festival version of the calendar, the months were named after the chief of the festival that corresponded to the lunar cycle. The years were also named after an administrator, the eponymous archon, who had served that year.
Months that had thirty days in them were referred to as Full months while months with twenty-nine days were referred to as Hollow months. This was due to the lunar cycle, and that two lunar cycles was approximately 59.06 days to them. There is additional evidence to suggest that the Attic months can be aligned with the months we have now for comparison. Such is as follows:

1	Hekatombaiṓn	July–August
2	Metageitniṓn	August–September
3	Boedromiṓn	September–October
4	Pyanepsiṓn	October–November
5	Maimakteriṓn	November–December
6	Poseideṓn	December–January
7	Gameliṓn	January–February
8	Anthesteriṓn	February–March
9	Elapheboliṓn	March–April
10	Mounichiṓn	April–May
11	Thargeliṓn	May–June
12	Skirophoriṓn	June–July

Civil calendar

Along with the festival calendar, the Athenian calendar had a civil calendar that coexisted and was based upon the prytanies. These months were thirty-six or thirty-seven days long and divided into a group of six pytranies and a group of four. This then created a ten month calendar that could be used to refer to time as well as the twelve month calendar.
The main reason this calendar existed was to keep track of the financial transactions within the Assembly. Each month last between thirty-five and thirty-eight days that made up the additional months in the festival calendar and ran from midsummer to midsummer. However, due to the number of tribes changing constantly, this calendar changed with them. Hence the separation between the festivals and a financial calendar. Many accounts of the financial calendar comes from various writings and inscriptions from the reigns of Archons. All evidence of the calendars supports the theory that the Athenians never aligned their calendars or devised a system to draw links between certain days. Scholars assume that people referred to the calendars separately for different occasions with different people.

1	Eréktheis
2	Aigís
3	Pandiṓnēs
4	Leontḗs
5	Akamántēs
6	Oinḗ
7	Kekrópēs
8	Hippothṓntēs
9	Aiántēs
10	Antiókhēs

Boeotian

The history on the Boeotian calendar is very limited as not many detailed records were kept. All months were named, numbered, and adjusted according to the seasons to fit the lunar year. A calendar was used as a reference in archaic times that bore resemblance to better known Greek city-states and their calendar systems. Any early evidence of the Boeotian calendar comes from Hesiod and is debated for interpretation. Hesiod's recollection of the months includes only one and this does not appear on any of the other calendars associated with Boeotia. This gap in information suggests to scholars a change in the organizing of months between the archaic and classic times in Boeotia. As most other regions in Greece, Boeotia divided their calendar months into thirds, but had differing ways to count the days. One system represented the days by ordinal numbers, another used common Greek terms to divide the months in half, and the third system indicated a division of the month into decads. With such a diversity in how the months themselves were categorized, it is hard for historians to give a definitive answer on the calendar.

1	Bukátios
2	Hermaíos
3	Prostatḗrios
4	Agriṓnios
5	Thiouios
6	Homolṓios
7	Theiloúthios
8	Hippodrómios
9	Pánamos
10	Pamboiṓtios
11	Damátrios
12	Alalkoménios or Alkuménios	or