Chronology of the Flood

Introduction

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The Overall Chronology

Chapters 7-8 of Bereshit describe the flood at length, providing a detailed dating of many of its stages.  The event took place over a period of about twelve months, with the flood beginning on the 17th of the second month and ending a little over a year later, on the 27th of the second month.  The text shares other significant dates and time periods as well:

• Dates – The ark landed on the 17th of the seventh month (8:4), the mountain tops appeared on the 1st of the tenth month (8:5), and the land dried on the 1st of the first month (8:13).
• Time frames – The chapters mention 40 days of rain (7:12, 17), 150 days of increasing waters (7:24) and 150 days in which they decreased (8:3), a 40 day wait before Noach opens his window (8:6) and then 14 or 21 days worth of sending the birds (8:7-11).¹

It is not clear, though, how all these dates work together and how the various events fit into the time frames allotted for them.

The table below summarizes the dates and time frames:

EN/HEע/E

תאריכים ומערכת של זמנים	המאורע
י"ז לחודש השני	התחלת המבול (ז:יא)
40 יום	גשם (ז:יב,יז)
150 יום	"ויגברו המים על הארץ" (ז:כד)
150 יום	"ויחסרו המים מקצה 150 יום" (ח:ג)
י"ז לחודש השביעי	התבה נחה על הררי אררט (ח:ד)
א' לחודש העשירי	"נראו ראשי ההרים" (ח:ה)
40 יום	לפני שפתח נח את חלון התיבה (ח:ו)
7 יום (ב' או ג' פעמים)	שליחות העורב והיונים (ח:ז-יב)
א' לחודש הראשון	"חרבו המים מעל הארץ" (ח:יג)
כ"ז לחודש השני	"יבשה הארץ" (ח:יד)

Dates and Time-frame	Event
17th of the second month	Beginning of flood (7:11)
40 days	Rain (7:12, 17)
150 days	"The waters were strong upon the earth" (7:24)
150 days	"And the waters decreased after 150 days..." (8:3)
17th of seventh month	Landing of the ark (8:4)
1st of tenth month	Appearance of mountain tops (8:5)
40 days	Before opening the window (8:6)
7 days (x2 or 3)	Sending of raven and doves (8:7-12)
1st of first month	Removing of ark's cover and drying of the land (8:13)
27th of second month	Land dries and Noach leaves ark (8:14)

Overlapping events

If all of the various time frames mentioned represent distinct periods of time, they do not fit into the allotted year,² suggesting that some of them must overlap.  However, the text does not clarify which might overlap:

• Are the 40 days of rain included in the 150 days of strong waters, or do they precede them, as might be assumed if the verses are sequential?
• Were there really two distinct sets of 150 days, or does the text simply mean that the waters decreased after the initial 150 days?  If the former, one would have expected the end of the second set to coincide either with the drying of the land on the 1st of the first month or the end of the flood on 27th of the second month. However, neither date works with the chronology given in the verses.

Specific events

• Landing of the Ark – As the ark could not land until the waters began to recede, how do 150 days, let alone 190,³ fit into the period between 17th of the second month (the start of the flood) and the 17th of the seventh month (when the ark landed)?  In a fixed Hebrew lunar calendar, where months alternate between 29 and 30 days, there is at most 147-149 days in any five month period,⁴ so neither option would seem to work with the text!
• Sending of the birds – The text (8:6) states that the birds were sent "after forty days", and the immediately aforementioned event is the appearance of the mountains tops on the 1st of the tenth month (8:5). However, if they were sent forty days after the mountain summits were already visible, why could the first dove not find a resting place?  In addition, this dating would leave about a month after their return before Noach removed the cover of the ark and the drying of the land on the 1st of the first month (8:13), making one wonder why he waited.⁵

The Approaches page will lay forth several possible reconstructions of the chronology of the flood in an attempt to answer the above questions.

¹ The verses do not say how long Noach waited between sending the raven and sending the first dove. If the dove was sent immediately, then the text allots fourteen days for the three birds' mission. However, before sending the second dove, the verse reads, "וַיָּחֶל עוֹד שִׁבְעַת יָמִים", suggesting that before the first dove had departed, Noach has also waited a week. If so, the events took place over 21 days.

² 40 days of rain, plus 2 sets of 150 days, plus another 40 days of waiting and at least 14 days worth of sending of birds equals 394 days, while the entire flood was only a year and ten days.

³ If the forty days of rain are distinct from the 150 days of increasing waters, there would be 190 days.

⁴ This depends on whether the beginning and ending dates (in our case, the 17th of the second month and 17th of the seventh month) are both included in the count, whether the year is counted from Tishrei or Nissan, and whether it is a "full" or "regular" year.

• If one assumes that the flood dates are counted from Nissan, and one includes both the beginning and end dates in the count, there are 148 days. If, though, only one end date is included there are 147 days.
• If one posits that the year began in Tishrei, included the final date of the 17th of the seventh month and that both Marcheshvan and Kislev had 30 days, there would be 149 days in this five month period. On the other hand, if one does not include the end date of the 17th of the seventh month and assumes that this is a regular year in which all the months alternate between 29-30 days, there would be only 147 days. Finally, if only one or the other assumption is true, one would get to 148 days.

⁵ An earlier dating, though, would require one to posit achronology in the text.