Bible Question:

What calendar was used in Genesis 7-8?

Bible Answer:

The question we are concerned with is, “What calendar was used in Genesis 7-8?” We will examine what the Bible reveals in order to reach our conclusion. The first relevant passage is Genesis 7:11.

In the six hundredth year of Noah’s life, in the second month, on the seventeenth day of the month, on the same day all the fountains of the great deep burst open, and the floodgates of the sky were opened. Genesis 7:11 (NASB)

Evening Of The Deluge

Flood Started In The Six Hundredth Year

Since we mark time in terms of years, months and days, Genesis 7 and 8 describes the duration of the flood using years, months and days. Consequently, Genesis 7:11 states that the flood started in the six-hundredth year of Noah’s life. That is, Noah was 600 years old when the flood started. This raises an important question, “What calendar was used at the time of the flood?”

First Option  – Hebrew Calendar Was used

The first option is that the Hebrew calendar was in use at the time of the flood. Since Moses wrote the book of Genesis, he would have been familiar with the calendar because it was in use at the time of Moses. But this must be rejected since the Hebrew calendar is a lunar calendar and its months vary in length between 29 or 30 days. Our reasoning follows in the next paragraph.

A quick comparison of Genesis 7:11 with Genesis 8:4 reveals that five months had elapsed from the start of the flood to the time that God shut off the outpouring of the water. Genesis 8:3 says that one hundred and fifty days had elapsed between Genesis 7:11 and Genesis 8:4. If we divide one hundred and fifty days by five months we discover that each month had thirty days. Since the Hebrew calendar was a lunar calendar, having 29 or 30 days per month for a total of 354 days per year,[1] this would suggest that the Hebrew calendar was not used in the book of Genesis at the time of the flood. It is important to note that any sequence of five months in the Hebrew calendar is less than one hundred and fifty days.

Second Option – Calendar Was Noah’s Life

The second option is that the passage of years, months and days after the flood were marked according to Noah’s life. This appears to be the correct conclusion. Even though this manner of marking time is foreign to us, it is most likely the correct option since the births of the patriarchs are marked in the genealogies according to the length of the lives of the patriarchs. Here is an example from Genesis 5.

When Adam had lived one hundred and thirty years, he became the father of a son in his own likeness, according to his image, and named him Seth. Then the days of Adam after he became the father of Seth were eight hundred years, and he had other sons and daughters. So all the days that Adam lived were nine hundred and thirty years, and he died.

Seth lived one hundred and five years, and became the father of Enosh. Then Seth lived eight hundred and seven years after he became the father of Enosh, and he had other sons and daughters. So all the days of Seth were nine hundred and twelve years, and he died. Genesis 5:3-8 (NASB)

Another example of referencing time according to the years of someone significant’s life also occurred in Genesis 14:5. This suggests that after the flood the calendar years, months and days  were referenced according to the life of Noah. Even if one objects to the above rationale, it is obvious from Genesis 7 and 8 that the flood was referenced to Noah’s life.

Flood Started In The Second Month

Genesis 7:11 states that the flood started in the second month of Noah’s six hundredth year. The plain sense reading is that the second month is the second month in Noah’s life after his birth month.

Keil and Delitzsch write that the months in Genesis 7 and 8 were not the religious months in the Hebrew calendar but the months according to the civil calendar. The religious calendar starts in Nisan (March/April) and the civil calendar starts in Trishi (September/October).[3] Then they conclude that the flood started in “the autumn at the beginning of sowing, or the autumnal equinox; so that the flood would be pouring upon the earth in October and November.” While the authors do not give a reason for this conclusion, it appears they have assumed that the new year in Genesis 7 and 8 corresponded with the Hebrew civil calendar, presumably established by God later in Exodus 12:2 and 13:4.

But this conclusion is wrong since there are no statements in either Genesis 7 or 8 that support the conclusion the flood started in the winter or in some other part of the year. It was a guess. Both Jewish and Christian scholars agree that the seasonal time of the year is uncertain. For example, Nahum Sarna, the Jewish author of a commentary on Genesis, states that “Whether the New Year fell in the fall or the spring is a matter of dispute in Rosh Ha-Shanah 10b-11b.”[4] Henry Morris, a Christian expert on the Genesis flood, writes that the exact date for the beginning of the flood is “found to be uncertain.” Both authors are correct. There is no strong or even weak evidence that supports a conclusion as to which part of our calendar year (Gregorian calendar) the months mentioned in Genesis 7 and 8 occurred. It is simply guesswork.

Flood Started On The Seventeenth Day

The days mentioned in Genesis 7 and 8 do not provide us any guidance in determining the time of year or the year in which the flood occurred.


The difficulty with Genesis 7 and 8 is that the book of Genesis never gives us any of the names of the months. Neither are there any references to any calendar year from either the Hebrew, Egyptian, Canaanite or any other calendar in use at that time. The reason for this is that immediately after the flood there were no civilizations. Noah and his family were the only people on the face of the earth. Therefore, Scripture uses Noah’s life as the calendar just as the pre-flood civilization used the length of the patriarchs’ lives to mark time (see Genesis 5). Most likely the months of Noah’s life continued to be used as the calendar until Exodus. This is an assumption. However, the length of the months changed due to the slowing of the earth’s rotation, which resulted in the lunar calendar and the eventual adoption of the Hebrew calendar. For more information read, “Was Jesus resurrected on the same day Noah’s ark rested on Mt. Ararat?”



1. Jack Finegan. Handbook of Biblical Chronology. Hendrickson Publishing. 1998. p. 31, Section 61.
2. Keil and Delitzsch. Pentateuch. Commentary on the Old Testament. Hendrickson Publishers. 2006. vol. 1. p.p. 91-92.
3. Finegan. Ibid. p. 80, Section 170.
4. Nahum Sarna. Genesis. The JPS Torah Commentary. The Jewish Publication Society. 1989. p. 55.
5. Henry Morris. The Genesis Record. Baker Book House. 1988. pp. 209.

Suggested Links:

Was Jesus resurrected on the same day Noah’s ark rested on Mt. Ararat?
The Flood, part 1
The Flood, part 2