The New Year and calendar in Ancient Mesopotamia

24 December 2017

In our Gregorian calendar, which has been in force since 1582, the counting of years adopts as its starting point the dawn of the Christian era, which is to say the (estimated) date of birth of Jesus Christ. It is a solar calendar, with months lasting 28 to 31 days, and the New Year falling on 1 January. So what kind of calendar was used in ancient Mesopotamia?

The Mesopotamian calendar was based on natural time intervals that characterise the progress of the Sun, the cycle of seasons and the motion of the Moon in the heavens. It was a luni-solar calendar with a solar year and lunar months, a system that was not without its problems. The solar year is defined by the successive return of the seasons: it equates to the time the Earth spends completing a full circuit around the Sun. In Assyria and Babylon in the first millennium BCE, the New Year was celebrated on the day of the spring equinox (March-April). But in the third and second millennia, calendars differed depending on the town and period under consideration. For example, at Ebla (Syria, twenty-fourth century BCE), the New Year began at the moment of the autumn equinox. Likewise, in the case of the Upper Mesopotamian Kingdom at the beginning of the second millennium, prior to Zimrī-Lîm, the King of Mari in the first half of the eighteenth century BCE, the decision was made to revert to the ancient calendar and to have the shift to the New Year occur at the moment of the spring equinox. At Aššur, in the same historical era, the New Year commenced with the winter solstice.

To keep track of the passage of time, the Mesopotamians referred to the years of their sovereigns’ reigns in accordance with three different systems. In southern Mesopotamia in the third millennium BCE and at Babylon at the beginning of the second millennium, the name of the year referred to an event that occurred in the previous year and glorified the king’s achievements: a military victory, major construction work, or a particularly pious act. At Aššur, at the beginning of the second millennium and in the Assyrian empire of the first millennium, the year took its name from a dignitary designated as a namesake. In both cases, today it is very difficult to arrange the years in order when one is not in possession of lists that furnish the sequence of the names of the years or of the namesakes. In Babylon, starting in the second millennium BCE, the years of reigns are numbered starting from the beginning of the king’s reign. It is only from 311 BCE onwards that just one way of counting the years was used, beginning with the accession to the throne of Seleucus I.

A lunar month is defined as the length of time that elapses between two successive New Moons appearing on the horizon just after the sunset. This phenomenon is not always easy to observe. It was therefore difficult to decide whether the month in progress was composed of 29 rather than 30 days. This division (of the year) into months remained empirical until the second half of the first millennium BCE, when ephemeris tables were drawn up that made it possible to set a date for the start of a month. The months were designated in accordance with the activities that were carried out during them, whether agricultural or religious; they varied from city to city, which is rather unhelpful to today’s historians.

The use of lunar months and a solar year creates problems with respect to synchronisation. Indeed, twelve lunar months composed of 29 or 30 days correspond to 354 days, meaning that there is a shortfall of eleven days to complete a solar year composed of 365 days. In order to make up for the shortfall, the Mesopotamians intercalated time and added a thirteenth month. The decision to add a month to the year underway was the duty of the king and was based on observation. It was only around 400 BCE that a mathematical pattern was found that established a correlation between 19 solar years and 235 lunar months, and hence the addition of seven intercalated months over the course of 19 years.

Even if the western world prepares to celebrate the New Year on 1 January, the Iranians and the Kurds still celebrate the arrival of spring. In China, according to the luni-solar calendar which is in force, the New Year begins between 21 January and 19 February on our Western calendar, when the second New Moon appears following the winter solstice. As for the Hebrew calendar, the New Year begins in the month of Tishri which, depending on the year concerned, falls in September or October of the Gregorian calendar. In the Islamic calendar, the first day of the year commemorates Hegira (the year 622 on the Gregorian calendar); according to the lunar calendar in force, this festival shifted forward by eleven days each year in relation to the Gregorian calendar.

Whatever the date of the New Year, let us all hope that that it falls under the peace sign!

Online conference: ‘Time expressed in Near Eastern cuneiform: chronology, measurement and calendars’, December 2017, Paris Diderot: Time’s pulse, transdisciplinary encounters at the Centre for Life Studies, Humanities Institute, Paris (under the directorship of Jean-Claude Ameisen).