The neomenia: the first thread of Moon that opens the month
From the Greek noumenia to the Roman kalends, from Rosh Chodesh to the Islamic hilal: how sighting the first crescent founded the month in many cultures.
For most of human history the month did not begin on a calendar page but in the evening sky. The decisive moment was the appearance of the first, very thin crescent after the days of invisible moon. This instant, called neomenia, from the Greek for «new moon», regulated rites, markets and religious feasts in civilisations very distant from one another.
The invisible moon
From an astronomical point of view, new moon is the moment when the Moon and the Sun have the same longitude on the ecliptic. At that instant the Moon is invisible, and it usually remains so for one or two days, until it moves far enough from the Sun to show a thin crescent just after sunset. The visibility of the first crescent depends on its angular distance from the Sun, the transparency of the air, the latitude and the season.
Kalends and noumeniai
In many ancient civilisations the month began with this first appearance. In Babylon it began on the evening when the crescent became visible, and astronomers tried to predict it with ever more refined calculations. In Greece the first day of the month was called noumenia and was devoted to household rites and offerings to the gods; in Athens it was regarded as a sacred day, on which no public assemblies were held.
The Latin name of the kalends recalls a similar practice. According to Macrobius, in the Saturnalia, in archaic times a minor pontiff watched the sky and, on sighting the new Moon, summoned the people to the Capitol to announce how many days remained until the nones. From the verb calare, «to call», the name of the first day of the month is said to derive, and it remained in the Roman calendar even after this had become detached from the lunar phases.
Rosh Chodesh and the hilal
In Jewish tradition the new month, Rosh Chodesh, was proclaimed by the court in Jerusalem on the basis of the testimony of witnesses who had seen the crescent. The Mishnah, in the tractate Rosh Hashanah, describes how the news was spread by fires lit on the hilltops, starting from the Mount of Olives. Later, with the adoption of a calculated calendar, which tradition dates to the fourth century, direct observation ceased to be necessary.
In Islam the lunar month still begins today, in many communities, with the sighting of the hilal, the first crescent. The practice is particularly important for the beginning and end of Ramadan, and it is not unusual for different countries to celebrate the feasts on different days, according to where and when the crescent is seen or is estimated to be visible. Other countries have adopted calendars based on astronomical calculation.
The symbol of beginning
The evening crescent has become a powerful symbol of beginning and renewal. In Mesopotamia the crescent was the emblem of the moon god Sin, worshipped at Ur and Harran, and it appears on countless seals and stelae. In the Greek and Roman world the crescent adorned the heads of Selene and Diana. In tradition the new moon was considered propitious for whatever had to grow, an idea found again in agricultural calendars and popular beliefs.
The neomenia reminds us that time, for our ancestors, was something to be observed together before it was calculated. The gaze turned westwards after sunset, waiting for a thread of light, united astronomers, priests and ordinary people in a shared gesture, repeated every month for thousands of years.