The word ‘month’ is cognate with the Greek and Latin terms it translates: they all come from Proto-Indo-European *mḗh₁n̥s. In Greek, this is reflected as mḗn, in Latin as mensis. That said, the words do not carry precisely the same meaning in all three languages.
In Greek, as the Stoic astronomer Cleomedes explains, mḗn can have several different meanings:
Mḗn is said in four different meanings. The goddess (i.e., the celestial body itself) is called mḗn she is sickle-shaped; and so is the condition of the wind (i.e., the weather) from new moon to new moon, as we are wont to say that the month (mḗn) was scorching or temperate. The period of time from new moon to new moon is also called a month, and so is any other period of thirty days, as when we say that someone was away or at home for a month, by which we do not mean from new moon to new moon, but simply the number of thirty days. Now, the first two are bodies, i.e., both the mḗn-shaped goddess and the condition of the air, while the latter two are incorporeal, because time itself is incorporeal.
What is especially interesting is that mḗn, unlike Selene (or her more poetic name, Mene), is masculine, even if it refers, as Cleomedes says, to “the goddess”. In Asia Minor, Men was often treated as the moon’s proper name, and as a male god. Alternately, he could be seen as the god ‘Month’, as in the Platonic philosopher Proclus of Lycia, since the Months, like other periods of times, were seen as gods:
Now, as Men, who is a god set up over the moon, makes the month (mḗn) subsist as a certain number in the revolution of the moon, and as the Horae generate the apparent measures of the seasons (hо̄raí) … (On the Republic vol. 2 p. 16)
According to commen conception, the Horae are goddesses, and Men is a god, and rituals for these have been handed down to us; we also say that Hemera (‘day’) and Nyx (‘night’) are goddesses, and we possess invocations for them given out by the gods themselves – so how much more must Chronos (‘time’), who encompasses all these, be a god? (On the Timaeus vol. 3 p. 32)
We say that the Horae (‘seasons’) and Menes (‘months’) are divine beings in the sense that they have divine lives (=souls) and divine intellects set up over them. (On the Timaeus vol. 3 p. 36)
Rituals for Men have been handed down to us from the Greeks, and among the Phrygians, Sabazios is hymned as Men in the midst of the initiations (teletaí) of Sabazios. For when people first observed that he measured the eternal revolution, they concluded that he was a god and honored him with initiations and every sacred worship, just like the Horae. (On the Timaeus vol. 3 p. 41)
The Latin mens, by contrast, only has the incorporeal meanings noted by Cleomedes – a lunar month or any period of thirty days – and another, more familiar to us today: a month defined purely by convention, without reference to the movement of the moon. In the classical Greek context, by contrast, months retained their lunar character. The Greek lexicographer Julius Pollux gives us a good idea of this:
The parts of the month are the waxing, the middle, and the waning, and so we divide it into three decads (periods of ten days). The Noumenia (new moon) and the second day up to the first decad (tenth day) must be attributed to the waxing part.
After the tenth, Hesiod says ‘the middle fifth’ (Works and Days 782), meaning the fifteenth day, but we should say ‘the first after ten’, ‘second after ten’, and so on until the eikás (eikad, twentieth day), and after that, ‘first after eikás’ – which is the ‘ninth of the waning’ – and ‘second after eikás’ – which is the ‘ninth of the waning’ – and so on to the triakás (thirtieth day), which the Athenians call hénē kai néa (old and new), and Homer designates ‘of the waning and waxing month at once’.
When one is diving the month into three, each third can be called a dekhḗmeron (ten-day period).
In brief, the precise method of counting varies (most strikingly, the last decad may be counted backwards), but the basic structure remains, and is tied to the appearance of the new moon, which is celebrated by a Noumenia celebration. Yet by the later Roman period, while the Noumenia were still observed, presumably at the time that the new moon was sighted (Marinus, Life of Proclus 19), the Greek names of the months became equated with the Roman months, which were standardized across the empire, and counted consecutively, even in Athens: “Proclus [died] on the seventeenth day of the month Mounychion, or the seventeenth of April” (ibid. 36).
The Roman months should thus not only be of interest to those who engage with ancient Roman traditions, but also those who consider the longue durée of Greek polytheism, at Athens and elsewhere, as all Greek cities within the empire were slowly transformed by the temporal (and festival) regime of Rome. The Attic calendar, by contrast, although studied by ancient scholars across the Mediterranean as an important legacy of classical Athens, was never adopted by other cities. Hence, as Julian Hellenism seeks to incorporate the broad sweep of Greco-Roman culture, the reconstruction of the pre-Hellenistic Attic calendar (which is, in its own right, a perfectly legitimate path) plays at best a marginal role in our project.
It is because of its transregional character, then, and not because we hold it in higher esteem, that we here focus in on the Roman calendar, but set aside the regional calendars of the Greek cities, Egyptian cities, and so on. One of the clearest Roman accounts is that of Censorinus (De die natali 22):
There are two genera of months: natural and civic. There are two species of natural months, as some are said to be solar, others lunar. A solar month is when the sun travels through one sign of the zodiac. A lunar month is a the particular period of time from new moon to new moon. Civic months, on the other hand, are certains numbers of days which a given state observes according to its institutions, as the Romans now do from Kalends to Kalends. The natural months are more ancient and common to all peoples, while the civic ones were instituted later and pertain to a single state.
The celestial months, whether solar or lunar, are neither perfectly equal nor consist in whole days. The sun, for example, remains in Aquarius for about thirty-one days, in Piscis [!] for around thirty, in Aries thirty-one, in Gemini almost thirty-two, and so on, differently in each. But while it divides its year – i.e., its 365 some fraction still undetermined by the astronomers – into twelve (equal months), it does not contain (only) whole days in each. And the moon completes its individual months in about twenty-nine and a half days; but these too are unequal among themselves, some being longer, some shorter.
The months of states, by contrast, vary in the number of days, but they always consists of whole days. Among the Albans, March is thirty-six days, May twenty-two, Sextilis (August) eighteen, September sixteen. The Quintilis (July) of the Etruscans has thirty-six days, their October thirty-two, and the October among the Aricini, thirty-nine. Those who assimilate the civic months to the course of the moon, like most cities in Greece, seem to have strayed the least; with them, every second month is made to consist in thirty days.
Our own ancestors followed this, when they used to have a year of 345 days. But the divus Julius (the god Caesar), who saw that in this manner, the moons did not agree with the moon, nor the years with the sun, as they should, chose to correct the year, so that the civic months should agree with the solar ones – albeit not each individually, but taken together at the end of the year.
Fulvius and Junius write that Romulus gave the names to ten original months. And he named the first two after his parents, March after his father Mars, and April after Aphrodite, that is, Venus, as his ancestors were said to originate from her. The next two, from the people: May from those who were older (maiores) in age, June from those who were junior. The rest were each named after their order: from Quintilis (quinque = five) to December (decem = ten).
But Varro teaches us, very clearly, that the Romans received the names of the months from the Latins, and he considers their inventors to have been more ancient than the city. Thus, he believes that the month of March is indeed named after Mars, but not because he was the father of Romulus, but because the Latin people were warlike; but April not after Aphrodite, but from aperiendo (‘opening’), because at this time, all things grow, and the nature of birth, which was closed, opens. May, further, received its name not from the maiores but from Maia, because both in Rome and previously in Latium, a ritual for Maia takes place in this month. June similarly is from Juno rather than from the iuniores, because people give special honor to Juno in this month. Quintilis, which among the Latins was the fifth month, and Sextilis and so on to December were named after the numbers. Januar and February were added later, but their names were still taken from Latium. January derived its name from Janus, to whom it was dedicated, February from februum.
A februum anything that expiates and purifies; februamenta are purgations, and februare is to purge and purify. But not everything of this sort is called a februum; because in other rituals, people ‘februate’, i.e., purify, in different ways. But in this month, at the Lupercalia, when Rome is purified, they use hot salt, which is called februum, and as such, the day of the Lupercialia was properly called dies februatus, and hence the month, February.
Of these twelve months, only two names have been changed. For the Quintilis was named July (after Julius Caesar) during the consulship of C. Caesar, for the fifth time, and M. Antonius, in the second year of the Julian (Caesar’s) era. And the month that used to be Sextilis was named August in honor of Augustus by senatorical decree during the consuilship of C. Marcius Censorinus and C. Asinius Gallus, in the twentieth year of Augustus. These names persist until today, for although many rulers after them have changed the names of certain months by calling them after their own names, they either changed them back themselves afterwards, or the old names were given back to the months after their deaths.
To this we may add, in conclusion, something from John Laurentius Lydus, who was a delightfully complex figure: a Lydian by descent and proud of this, but also a self-identified Roman; a native speaker of Greek; an inhabitant of Constantinople; a teacher of Latin. Like many late antique intellectuals with complicated ethnic backgrounds, he writes about the groups he could lay claim to as if he were an outsider to all of them (cf. the reference of “Greek” philosopher Proclus to ‘the Greeks’ above). He produced perhaps the most erudite, but also the most bizarre work on our subject, a Greek miscellany called On the Months, which contains the following section (chapter 3.22):
There are twelve months among all [peoples], but different nations name them differently.
The Athenians indeed [name them] as follows: Elaphêbôlion, Mounychiôn, Thargêliôn, Skirophoriôn, Hekatombaiôn, Metageitniôn, Boêdromiôn, Pyanepsiôn, Maimaktêriôn, Poseideôn, Gamêliôn, Anthestêriôn.
The Greeks, as follows: Gorpiaios, Hyperberetaios, Dios, Apellaios, Audonaios, Peritios, Dystros, Xanthikos, Artemisios, Daisios, Panemos, Lôos.
The Hebrews, as follows: Thesri, Marsechouban, Khaseleth, Tebeth, Saphat, Adar, Nisan, Iar, Siban, Thamous, Aab, Eloul.
The Egyptians, as follows: Thôth, Phaôphi, Athyr, Choiak, Tybi, Mechir, Phamenôth, Pharmouthi, Pachôn, Paÿni, Epiphi, Mesôri.
The Romans, as follows: September, October, November, December, January, February, March, April, May, June, July, August.
So much for the matter of the months among the [various] nations.
Now, the Babylonians and the Egyptians defined the beginning of the year as the Spring equinox, adopting, as it were from a head, the equinox in Aries on account of the fact that all perceptible nature grows in the Spring. The Greek tradition made the first degree of Cancer—as one might say, the 23rd of June—the beginning of the year.
But while these and all the other nations observed one single starting point of the year, the Romans [observed] three: one, “priestly,” a second, “ancestral,” and another, “cyclical and civic.”
The priestly [beginning] is in January, when the sun, passing Capricorn, causes an increase of the day.
The ancestral [beginning] is what they call the first of the month of March—when it is the Roman custom even to this day to “shake the weapons.”
The “civic” or rather “cyclical” [beginning] is the first of the month of September, which the Greeks call “apportionment” [epinemêsis], but they themselves call “indiction.” For indictio [is what] the Romans call the declaration of the yearly cycle in their ancestral language. Antiquity, you see, kept the cycle as the [period] they called a lustrum —that is, the period of five years —and there was a purification, and mysteries of the Mother were conducted at that [time]. Later on, however, they decided to renew their cycle after 15 years, in honor of Ares (and he was an ancestral god for the Romans, as they say). For the complete “restoration” of Ares [i.e., the planet Mars] is observed in two ways: a small one taking 15 [years] and a “middling” one taking 79.
That the Romans held the beginning of the year in March as an ancestral tradition is clear also from the fact that those they called “matrons”—that is, the well-born— entertain the household slaves [then], just as it was the custom for the property-owners to do this in the Kronia [i.e., Saturnalia]. The women serve the male household slaves, in honor of Ares, on account of their greater stature; the men, as it were offering an act of worship averting evil to Kronos, would serve their own slaves, so that they would not in reality suffer some sort of retribution and fall into enemy servitude.
(Translation of John Lydus from the translation of Mischa Hooker, slightly adapted; others courtesy of Ɔ. Martiana.)