Chronology & Dates
Ancient chronological methods
Beginning in the Early Dynastic period ca. 2400 BC, Babylonian scribes began to qualify administrative and legal texts with notations clearly identifiable as date notations, consisting of all of some of the categories Ruler, Year of rule, Month of year, Day of month. From the Late Uruk period of the latter third of the 4th millennium BC on, these calendars combined knowledge of solar and lunar cycles to achieve an ideal administrative year of 360 days divided into 12 months of 30 days each. The cultic calender evidently was based on the lunar cycle of ca. 29.5 days for each month, and therefore a lunar year of ca. 354 days and thus the need for intercalation of extra months on average every three years. These dates are currently entered to CDLI catalogue in the form RN.Y.M.D (Royal name is spelled in full with conventional English designations), with “–” for lost information, “00” when information was not given by the scribe. Month intercalation were designationed by scribes with "min," “the second,” or "diri," “extra.”
For defining the year and during the three millennia of Mesopotamian history, scribes used three different systems
1) Year names
This system attributes a “name” to the current year, making reference to an official event of the previous year (e.g., a military victory, the foundation of a religious establishment, etc.). This method was common during the Old Akkadian, Ur III, and Old Babylonian periods.
This system attributes the name of a "limmu” officer to the current year; this eponym, annually appointed, gives his name to the year in question. This method was the predominant system used in Assyria for more than a thousand years.
3) The counting of years
This system, counting the years of the reign of a sovereign, first began to be used during the ED IIIb period at Lagash and it became the norm in Babylonia from the middle of the second millennium BC until the Seleucid period. A similar system was used to count the years of the Seleucid era.
Other systems were maintained as well. These include lists of the reigns of kings and their genealogies, and a system structured around narrative and chronology, called palû, that was attested in Assyrian inscriptions.
Modern chronological models
- Astronomical observations
Calendars and month names. Seasonal and cultic calendars
The lunar month (iti in Sumerian, warḫu(m) in Akkadian) is defined as the interval of time between two successive apparitions of the first moon. The month begins the evening that the new crescent moon reappears for the first time on the Western horizon just after the setting of the sun. The lunar month consists of 29.53 days, 30 being the number symbolising the moon god. Although it was not always possible to observe the reappearance of the new crescent, the division of the month into 29 or 30 days remained empirical until the first millennium, when the calculations based on the ephemeral tables that took into account the different factors of visibility of the moon allowed the beginning of the month to be fixed.