Babylonian and Seleucid Dates

Intro page      |      How to Read the Tables      |      The Babylonian Calendar       |       Sources      |      Analysis

This page gives access to two conversion tables in Excel format (905 kB), with a copy in HTML format (2.57 MB), useful for determining the Julian equivalent of Babylonian and Seleucid civil dates in the Ptolemaic era. The dates of some important events early in the Ptolemaic era, such as the death of Alexander, and of a number of Seleucid events involving Ptolemaic princesses, can be determined from these tables.

Three tables are provided:

1) The standard conversion table generated by Parker & Dubberstein in 1956 (PD)
2) A corrected conversion table, consisting of PD overlaid by data from contemporary astronomical diaries, lunar tables, eclipse reports, eclipse predictions, goal year texts and horoscopes.
3) A difference table, showing the differences between the first two tables.

The second of these tables is also provided in a CSV text format.

The Structure of the Babylonian Calendar

The Babylonian calendar was a lunisolar calendar. The Babylonian day began at sunset, and each month notionally began with the first rising of the crescent moon; in essence, a Babylonian month was a synodic lunar month, represented as a 29 or 30 day month. Contemporary records show that the start of the month was actually determined by observation of the new moon wherever possible, or by prediction if not.

By this period, Babylonian astronomers had determined that 235 months lasted for almost exactly 19 solar years, and had developed a regular system of intercalation of embolimos months in such a way as to ensure that 1 Nisanu always began on the first crescent moon on or after the vernal equinox. J. P. Britton in J, M, steele, Calendars and Years 115 at 122f., suggests that this was a deliberate effect, returning to an Old Babylonian practice, though by modern calculations, 1 Nisanu was occasionally a day or two before the equinox. It is believed that the Seleucid and Parthian Macedonian calendars were also aligned to this system, and that it had been standardised by the Achaemenids for use throughout their empire. Although the first assumption is reflected in the tables, the evidence for both is slim. There is at least one datum that appears to contradict the second: the Elephantine Aramaic papyri implies a local Tashritu that was one month early in year 8 Darius II = 416/5.

Six of the embolimos months were inserted after Addaru, the last month of the year, at intervals of every second or third year. One was inserted after Ululu, half way through the year, every 19th year. Taking this to be the first year of a 19 year cycle, the exact Babylonian years in which embolimos months were intercalated are:

Ululu II: Year 1
Addaru II: Years 3, 6, 9, 11, 14 and 17

It is generally assumed that this allocation of intercalary months was also standardised througout the Achaemenid empire, and hence throughout Seleucid territories, although the Elephantine Aramaic papyri appear to imply a local Tashritu II or Arahsmanu II in year 8 Darius II = 416/5.

In the Macedonian variant of the cycle, as generally understood, intercalations occurred at the same time but in different cycle years, because of the half-year phase difference between the two. There are two years to relate the Macedonian cycle to the Babylonian one:

Hyperberetaios Embolimos: Year 1
Xandikos Embolimos: 4, 7, 10, 12, 15, and 18

Xandikos Embolimos: 3, 6, 9, 11, 14 and 17
Hyperberetaios Embolimos: Year 19

It should be noted that this theory, while generally held, and so represented in these tables for that reason, rests on remarkably little evidence. The correspondence of Macedonian month names to Babylonian ones were changed, at least in areas under Parthian rule, from some time before 48/7 B.C., until some time in the middle of the first century A.D. The standard system was certainly in use in Dura Europus in A.D. 31; on the other hand, the Parthian system is known at least as late as A.D. 49. This issue is discussed here. Under the Parthian system, Ululu II corresponds to a Gorpaios Embolimos, while Addaru II corresponds to a Dystros Embolimos.

Website © Chris Bennett, 2001-2011 -- All rights reserved