© 1999, Apollonius Sophistes

Remarks

1. This calendar is intended for those who want to observe the Sacred Month (Mên kata Theion), that is, the month according to Moon phase.
2. The principal source for the Sacred Month is Hesiod's Days (the last part, ll. 765-282, of the Works and Days), and M. L. West's comments thereon (M. L. West, Hesiod Works & Days, Edited with Prolegomena and Commentary, Oxford, 1978).
3. The ancient Greeks reckoned the day from sundown; that is, Tuesday begins at sundown Monday. The first day of the new month (Noumênía = New-Moon/Month) is supposed to coincide with the first sighting of the young crescent. This would be early in the evening following the 30th day (which is why it's called Hénê kai Néa = Old-and-New). Note that in modern almanacs, "new moon" refers to the conjunction of the Moon and Sun, that is, the dark of the Moon. For purposes of the Sacred Month, the New Moon (Noumênía) occurs a day or two after conjunction. (To appreciate the difficulty of calculating "first visibility" from conjunction, see O. Neugebauer, The Exact Sciences in Antiquity, 2nd. ed., Dover, 1969, pp. 106-9.) It may be simpler to use the system devised by Solon: the (Greek) day during which conjunction occurs is declared Old-and-New, the 30th; the following (Greek) day is then Noumênía, the 1st. That is, the first sundown after conjunction begins the 1st of the new month. If this system is followed, then the first quarter will fall on the 7th or 8th, the full moon on the 14th or 15th, and the third quarter on the 22nd or 23rd, depending on the exact time of conjunction; if the 1st is based on "first visibility" (as Hesiod probably did), the moon phases may fall a day earlier.
4. For Hollow Months (29 days), the 29th day is omitted, for Full Months (30 days), it's not. The 30th day is always included. This adjustment is made to ensure that conjunction occurs on Old-and-New (30th) or first visibility on Noumênía (1st).
5. The visible month may be divided into four weeks: 1-7, 8-14, 15-21, 22-28. However the ancient Greeks normally divided the month into two halves (Waxing and Waning) or into three decads (Waxing, Middle, Waning).
6. It will be observed that corresponding days in each decad often have similar deities, fortunes, etc.
7. Hesiod recommends different days for different activities (e.g., launching ships). I have included the ones that are easy to interpret more generally (e.g., release completed projects). However, if you want to know when to castrate your goats, you will have to consult Hesiod's text. As expected, the waxing part is better for starting things, the waning part for finishing them; overall the waxing half is more auspicious.
8. Certain days have special names, which are given after their numbers. In addition to those already mentioned, there are Tritomênís = Third-of-month, Tetrás = Fourth, Dikhomênía = Mid-month (Full-moon), Eikás = Twentieth, Triseinás = Thrice-ninth, Triakás = Thirtieth. Although the 15th is officially "full moon," it may occur a day or two earlier.
9. Numbers: In the ancient Greek manner, days in the first decad may be specified "the second of the waxing (moon)" or "the waxing second," etc. Days in the second decad may be specified "middle first" to "middle tenth" or "eleventh," "twelfth," "three and tenth," up to "nine and tenth," then "twentieth." The last decad may be indicated by absolute position ("twenty-third") or relative position ("waning third," "the third after the twentieth"), but is normally counted down to the New Moon (indicated by a negative number in parentheses), "waning eighth." Note that "waning third" could be either the 23rd or the 28th (-3); this ambiguity complicates interpreting Hesiod's text. When counting down, the "earlier tenth" is the 20th and the "later tenth" is the 21st, since the 10th is specified as the "waxing tenth."
10. Here are some general guidelines if you follow Solon's system: Look up the time of conjunction in an almanac. If it is between midnight and dusk, then Old-and-New (30th) is that calendar day, and the full moon is on the 15th (Dikhomênía). Otherwise, if conjunction is between dusk and midnight, then Old-and-New is on the following calendar day, and the full moon is on the 14th, although it won't be visible until the 15th begins at dusk. If conjunction is between dawn and dusk, the month is full, otherwise it's hollow.