Sermon on the Mount, The Emmaus View

Appendix B: The Chronology of the Noahic Flood (Version 1.7 )

In the Genesis flood (Gen 7:4-8:13) we find God composing poetry with the ink of history, for the flood’s periods, are arranged in a chiasmus (7, 40, 150, 150, 40, 7) that highlights the moment when God remembered Noah as the flood’s most significant point. Onto this perfect looking symmetry are bolted a further 7-day period and a curiously long delay, of two months twenty-seven days, before Noah establishes a covenant with his deity (see table below).



Start Date

Period in days

7:4, 11

7 more days, then rain


7:4, 11-12, 17

40 days and nights of rain





Water prevails for 150 days


8:1, 4

God remembers Noah and ark rests on Ararat




Water recedes for 150 days
(mountain tops appear on 1/10)



40 days then send raven and dove



Wait 7 days & send a dove
(end of symmetric portion)



Wait 7 days & send a dove



Land habitable, remove the cover




Land is dry, Noah’s sacrifice



It is common to assume that each 40-day period is included within its adjacent 150-day period. Thus, from 150 days spanning five months one may deduce that the flood account uses a calendar with a consistent month length of thirty days.

Whilst the flood’s periods may suggest a thirty-day month, it is worth reflecting that

Ancient calendars were often based on a 354-day lunar year and, as the lunar month varies, most were governed by observing new moons. Moses recognised such new moon festivals, one of which was in the seventh month (Num 29:6), and, in the time of Saul, they could last at least two days (1 Sam 20:27), as required for synchronising 29 and 30-day months. In the contemporary Hebrew calendar the boundary between the eighth (Cheshvan) and ninth (Kislev) months is still determined by new moon observation. There may also be a single new moon festival featured in the Noah account, for on the first of the tenth month it mentions that the tops of the mountains could be seen (Gen 8:5). As the water had been abating for at least two months since the ark rested, at which point it had only covered the mountains by at most 15 cubits (about 6.75 meters, Gen 7:20) it is likely the mountaintops had been above water for some time. If so, then they presumably remained hidden by clouds, making the mountains appearance on the first of the tenth notable, not because they broke the water on that day, but because the improving visibility that allowed them to be seen also permitted observation of the new moon.

We may refining the observation that Noah may have used a 354 day calendar by recalling that Genesis 2:1-3 portrays the seven-day Sabbath cycle as the foundational unit of timekeeping prior to the flood. Evidence that this was the case may be found within the flood account itself1. Not only is it full of seven-day pauses, but also the same word used for the ark’s rest on Ararat (Gen 8:4) is used for God’s seventh day rest (Exod 20:110) and the rest associated with the Sabbath regulations (Exod 23:12). If you assume that each of the flood’s 150-day periods overlapped with the adjacent periods at both ends, then the Hebrew habit of counting part days as whole ones shortens the total of the periods so that the ark’s opening on the first of the first falls on day 355. Moreover, if you start the flood on a Sabbath and assume the flood’s dates use a particular lunar calendar (with equal numbers of 29 and 30 day months2), you can arrange the month lengths such that significant events when God interacts with Noah fall on Sabbaths and each seven-day delay corresponds to a Sabbath cycle.

Assume an alternation of 30 then 29-day months and the neat Sabbath correspondence to dates and the necessary period durations are shown in the table below. The outcome of using alternating triplets of 30 and 29-day months as suggested by First Enoch (1 En. 78:14-17) is the same and these are probably not the only permutation of month lengths that give this result. However start the alternation with a 29-day month and it seems the Sabbaths no longer neatly fit with the dates.

The flood timetable and Sabbaths if a 364 day year is assumed. Calculated dates in parenthesis.



Event and ensuing period



God warns of rain in seven days



God seals the ark prior to waters rising for 5 months on the lunar calendar (147 days)



Ark rests prior to the waters receding for 147 days



Noah opens window prior to first delay of seven days



Noah sends out second dove prior to second delay of seven days



Noah sends out final dove and removes the cover prior to a delay of 50 days and a Sabbath



Noah establishes covenant with God at start of a new sacred year

The evidence presented above suggests that the timetable of the Genesis flood was governed by a lunar calendar, whose new-moon festivals Israel continued to observe post-inundation. However, there are indications that the flood-year witnessed the adoption of a quite different type of calendar.

Because the lunar year is on average approximately 10.9 days shorter than the solar year, its months get progressively out of sync with the agricultural seasons. For this reason, many ancient cultures adopted some form of lunisolar calendar. Such calendars typically used intercalary months (as in the Babylonian calendar) or additional annual days (as in the Egyptian civil calendar) to compensate for the difference and keep the months and the agricultural seasons in step3. However, God’s people needed a calendar that could provide both regularity of agricultural seasons and regularity of Sabbath based sacred festivals. The length of year best suited to achieve this is neither 354 nor 365 days, but 364.

In the first century B.C.E. the Qumran community used a 364-day, 52 Sabbath, calendar4. Such a calendar is also mentioned in literature from that period, these include the Qumran Temple Scroll (11QTemple) and the book of Jubilees (Jub. 6:32), whilst First Enoch describes both 364 and 354-day calendars (1 En. 72:32, 82:6, 78:14-17). However, within the Mosaic Law we find two strands of evidence that ancient Israel also used some form of 364-day calendar. Firstly, the Law assumes that certain major festivals will always fall in a regular relationship to Sabbaths (Lev 23:5-9, 39, 15-16). Secondly, the rules for sabbatical years and jubilees provide the longer-term adjustments needed in order to keep a 364-year system in sync with the solar year. The 364-day year lags behind the solar year by an average of about 1.24 days per annum, which means the cumulative error can only be corrected without disturbing the regularity of Sabbaths after six years have elapsed, by which time the difference is about 7.45 days. Thus, every seventh year could gain an extra week and become an extra-Sabbath year.

Even factoring in extra-Sabbath years the calendar still falls behind the sun by about 1.7 days in every Sabbath year cycle. With the seventh repeat clearly significant for days and years, the seventh Sabbath year, i.e. the forty-ninth year, would seem the ordained place for the next adjustment. However, by that time one would need to offset the Sabbath year’s end by eleven days, which is unfortunately not a whole number of Sabbaths. Therefore, the only way to keep Sabbaths and festivals in step across the forty-ninth to fiftieth year boundary was to abandon the old calendar and start again with a new one. That being the case, no other longer-term cycle was necessary, adjustments in the sabbath year and at the sabbath of sabbath were quite sufficient.

Isaiah helps us understand how Israel viewed the disruptive Jubilee calendar change, and in doing so he hints that Noah was also involved in a similar process. Having likened the Assyrian invasion of Judah and its aftermath to the Noahic flood and the new creation resulting from it (see Chapter 21), he goes on to assure Hezekiah that he will not loose Jerusalem. The sign will be that the land lies fallow in the ‘flood’ year and in the next, and then they will sow and reap, just as with a forty-ninth year and its following Jubilee. Hence, for Isaiah, Jubilee left the land like a new creation, with everything returned to how it had been at the outset, and that presumably included the calendar cycle. The forty-ninth year was therefore a year when God’s people, like Noah, lived off what they had stored up, the jubilee year that followed was like the aftermath of Noah’s flood, a time, as at the beginning, when God’s people had no debts and each possessed the land that God had given them.

Early Israel’s apparent use of a 364 day year and Isaiah’s link between the Noahic flood and a calendar restart is particularly interesting given the Noahic Covenant’s assurance of stable seasons (Gen 8:22). For Noah entered into his covenant on the twenty-seventh, effectively marking the start of a new year seventeen days after the anniversary of the flood process starting (on the tenth day). By imposing a distorted symmetry upon the flood (inserting an extra Sabbath) and then accepting Noah’s delay in sacrifice, God established the legal precedents needed for Noah to adopt a cultic system base on a 364-day year. It therefore looks as if Noah entered the flood year using a 354-day lunar calendar and emerged to a new covenant that used a 364-day lunisolar calendar.

The Qumran community used a base month of 30 days and a 31-day month at the end of each quarter5. However, if the extra four days were added at the end of the year, as were the extra five days in the Egyptian system6, then a 364-day system would appear to have the fixed 30-day month suggested by the flood’s periods. Moreover, assuming a regular alternation of 30 and 29-day months that starts with a 30-day month, the five month period before the flood’s most significant point is lengthened by three days, making the 147-day delay of the original lunar system look like a 150-day delay, yet keeping all the key dates the same (though dislodging them from the Sabbaths into the middle of weeks).

A flood-year switch of calendar may also go part way to accounting for the rather odd dates on which we are told the ark was sealed, it rested on Ararat, and Noah offered his sacrifice. The forty-ninth year of a 364-day system was 371 days long and would, assuming that the 354-day year ended on the same day, have started seventeen days earlier. Therefore, the original lunar-year dates of the sealing of the ark and the resting upon Ararat would have been seventeen days earlier and fallen on the first day of their respective months, i.e. on a new moon festival. Noah’s sacrifice would then have taken place ten days after the new moon.

Isaiah’s association of the Noahic flood with the forty-ninth year suggests an understanding of the origin of early Israel’s calendar. However, it is tempting to suppose that his insights were, to some extent, shared by at least one Maccabean author, for Jubilees, in addition to promoting a 364 day year, attempts to link new moon festivals to the events of the Noahic flood, and warns that failure to observe the feasts will disturb the seasons and dislodge the years (Jub 6.23-33).

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1 Richard L. Fix, "The Year of the Flood and Evidence Against Previous 30 Day Months and 360 Day Years", n.p. [cited 16 Nov 2009]. Online:

2 In practice their precise lengths were observational and the length of the synodic month, whilst averaging approximately 29.531 days, varies cyclically across the year by as much as fourteen hours (Ivr Bloomburg, “The Length of the Lunar Cycle,” n.p. [cited 15 May 2009] Online:

3 Francesca Rochburg-Halton, “Calendars: Ancient Near East”, ABD, 810-814.

4 James C. Vanderkam, “Calendars: Ancient Israelite and Early Jewish”, ABD, 814-819.

5 Vanderkam, “Calendars: Ancient Israelite and Early Jewish”, ABD, 814-819.

6 Rochburg-Halton, “Calendars: Ancient Near East”, ABD, 810-814.