When we read Genesis or Samuel/Kings/Chronicles (or any OT book that attempts any sort of reliable chronology), what are reasonable meanings of the word (translated) "year?"

Suppose I wanted to construct a timeline of the kings of Israel and Judah. Chronology in those books is typically stated as "in the _x_th year of the reign of King Y of Israel, Z was made king of Judah." Should I assume that the ancient Hebrew year meant 365.24 days (one solar year)? I know they used a lunar calendar, and so if all their months had 28(?) days, did they have 13 months? Did their years differ from ours approximately 5 days every 4 years? How should a historian reckon "years" in this kind of account?

I presume it is likely the same problem as the use of "years" in Genesis, since the years mentioned were most likely those used by the Hebrews at the time the text was written down. I realize this may not be so, but if it's not so, then it might be difficult to put any particular value to "a year" since we would have no frame of reference by which to assign a specific amount of time to one "year."


3 Answers 3


The ancient Hebrews used a lunar calendar; each month began with the sighting of the new crescent, and continued until the next sighting, which means that approximately half of the months had 29 days, and approximately half had 30. In order to keep the months in the correct seasons the Hebrews (like the Babylonians, Greeks etc.) must have practiced some form of intercalation, that is: they must have inserted a thirteenth month from time to time. However, there is no mention of intercalation in the Hebrew Bible, and the precise mechanics of the ancient Hebrew calendar are not actually known. The present-day Jewish (or Rabbinic) calendar has mathematical formulae for calculating the beginning of each month and for determining which years have twelve months and which have thirteen, but there is no evidence for this calendar before the 9th century of the Christian era.

The most recent discussion of this theme can be found in Calendars in Antiquity:Empires, States, and Societies by Sacha Stern, Oxford 2012; also Time, Astronomy, and Calendars in the Jewish Tradition, edited by Sacha Stern and Charles Burnett, Leiden 2014.

  • Any recommendation for how to reckon "years" in the text? Say I start with a known archaeological year, 576 BC. If I want to work backward using the text, what kind of adjustments might I need to make to account for the chronology in the text?
    – mojo
    Jun 16, 2014 at 15:39
  • Also, I know that is Islam, there is no correlation between the calendar and seasons. Do we know that the Hebrew calendar was different?
    – mojo
    Jun 16, 2014 at 15:57
  • The Islamic calendar is unique in this regard (lunar months but no intercalation). Jewish tradition associates Passover with the Spring (according to the traditional interpretation of the word aviv in Exodus 13:4; 23:15), so the Hebrews must have had a way to keep the festivals in time with the seasons.
    – fdb
    Jun 16, 2014 at 18:38
  • 2
    What has not really been resolved is what is meant by “in year N of king X”. Does the regnal year begin on the actual day of accession (as with the Romans), or on the new year’s day (presumably 1st of Nisan) after his accession (as with the Babylonians)? This is debated by Biblical scholars.
    – fdb
    Jun 16, 2014 at 18:39
  • 1
    @mojo The crux of matter with these ancient empirical calendars is that most dates (i.e., of the full moon) and time intervals (such as the length of a given year weren't reckoned at all. Instead, they were observed. So to determine, say, if a particular year had 13 months or 12, you'd need to check the written records kept by scribes from that time period. If the documents are lost, so too is the information.
    – David H
    Sep 8, 2014 at 9:32

The Essenes (headquartered in Qumran) used a solar calendar like the one described in Jubilees and 1 Enoch. Here, each of the twelve months had 30 days except for the last month of each quarter which had 31. This was a marked difference from the calendars of the mainstream Jews, and to set themselves apart is why they used this calendar.1 In one of their writings, they argue that theirs is a restoration and the mainstream Jews are using a flawed calendar.

The mainstream Jews at the time almost certainly used some kind of intercalation to keep the spring feasts in the spring and the fall feasts in the fall.

The question of how to figure the dates of the kings in Samuel/Kings/Chronicles has been the topic of doctoral dissertations. As fdb says, it is still debated.

1Flusser, David. The Spiritual History of the Dead Sea Sect. English Series edited by S. Himelstein and translated by C. Glucker. Tel-Aviv: MOD Books, 1989, 43

  • The Jubilees/Qumran calendar had years of exactly 364 days. As this number is evenly divisible by 7, any day of the year will always fall on the same weekday. The defect of this calendar is that it is about one and quarter days short of the tropical year. Thus, the months do not stay in the same seasons for very long.
    – fdb
    Jun 16, 2014 at 19:34

Yes, I believe we should assume that the ancient Hebrew year averaged out to 365.24 days, with some years of 354 days and some of 384 days.

Although the Bible does not explicitly mention intercalation (an added month), it is inferred in the name meaning of the first month of Abib. Abib simply means "tender, green ears" and refers to the ripening of the barley grain - the first harvest of the year. If a 13th month was not added approximately 3-yearly, the new year would start before the barley was ready to gather. Furthermore, each of the later festivals would slide behind their relevant harvests. (wheat, fruit, etc. Exodus 23:14-17)

Later in the history of Israel, the name of the first month was changed from 'Abib' to 'Nisan.' However, the religious festivals were always kept in the correct seasons from year to year. So, our conclusion must be that Israel's calendar was a soli-lunar system, tracking the revolutions of Sun as well as Moon.

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