The flood story in Genesis is one of the most precisely dated narratives in the Bible. However, the narrative counts time differently than modern calendars do. As a result, some readers find it challenging to convert the way Genesis marks time with the way people do it today. This difference leads many Bible readers to ask when Noah built the ark.
Scholars estimate that Noah built the ark 3,000 to 5,000 years ago. Some contend Noah finished it 1,656 years after creation, which comes from interpreting Genesis 1 as historical and believing that the genealogy in Genesis 5 has no gaps. Alternatively, non-historical interpretations lead to a wide range of dates.
What does Genesis reveal about Noah’s birth date? How old was Noah when the flood started? In what way does Genesis precisely date the flood story? How long did it take Noah to build the ark? Keep reading to learn the answers to these questions and others.
When was Noah born?
Calculating when Noah built the ark requires analyzing the genealogy in Genesis 5 and noting the dates that the flood story records in Genesis 6-9.
What clues does Genesis 5 give readers? Genesis 5 records a genealogy that lists the names and ages of Noah’s ancestors dating back to Adam. Using the numbers in the passage, readers can calculate the year of Noah’s birth in relation to creation and the other patriarchs. This method assumes there are no gaps in the genealogy, which some Genesis scholars, even conservative ones, don’t think is true.
What are “gaps” in a genealogy? Scholars disagree on if the genealogy in Genesis 5 includes “gaps,” which means that the list skips multiple generations, maybe even hundreds. Thus, some contend that there may be gaps of thousands of years between certain names, making it nearly impossible to know the exact dates of certain events before the flood. Those who believe there aren’t gaps simply add up the dates in the list.
|Name||Birth Year||Death Year|
*Genesis 5:24 teaches that Enoch never physically died but was taken to heaven: “Enoch walked with God, and he was not, for God took him” (ESV).
This dating method also contends that the “days” in the creation account are seven consecutive 24-hour periods. If the creation account is poetically describing a process of millions of years, then the method of calculating the ages of the patriarchs described above isn’t reliable.
How old was Noah when the flood started?
Genesis reveals that “Noah was six hundred years old when the flood of waters came upon the earth” (Gen. 7:6). Therefore, if Noah was born 1,056 years after creation and the flood started when he was 600 years old, and the ark took approximately a year to build (see below, then he was 1,655 years old when he began building the ark and 1,656 when he finished it.
Demonstrating extraordinary precision, the next time Genesis refers to Noah’s age, which it does in relation to floodwaters, marks it to the day. “In the six hundredth year of Noah’s life, in the second month, on the seventeenth day of the month, on that day all the fountains of the great deep burst forth, and the windows of the heavens were opened” (Gen. 7:11).
The next time Genesis mentions Noah’s age is also a reference to a specific day but a different year. Genesis 8:13 reads, “In the six hundred and first year, in the first month, the first day of the month, the waters were dried from off the earth. And Noah removed the covering of the ark and looked, and behold, the face of the ground was dry” (Gen. 8:13).
The final time Genesis mentions Noah’s age is another reference to him being 601 years old. Genesis 8:14 reads, “In the second month, on the twenty-seventh day of the month, the earth had dried out” (Gen. 8:14).
Other dates mentioned near the end of the flood story also use Noah’s age as a fixed date (see below).
|Event||Scripture||Year, Month, Day|
|God says the flood will start in 7 days||7:4||600, 2, 10|
|The flood starts||7:11||600, 2, 17|
|Last 40 days||7:12||600, 3, 27|
|The waters recede||8:4||600, 7, 17|
|The mountain peaks appear||8:5||600, 10, 1|
|Noah sends the raven||8:6||600, 11, 10|
|Noah sends the dove for a 2nd time||8:10||600, 11, 24|
|Noah sends the dove for a 3rd time||8:12||600, 12, 1|
|The flood waters dry up||8:13||601, 1, 1|
|Noah exits the ark||8:14||601, 2, 27|
Why does Genesis date the flood using Noah’s age?
The Gregorian calendar, the most common method of tracking time in the world today, marks years using the birth of Jesus Christ as its fixed point. Even the current practice of replacing B.C. (“Before Christ”) with B.C.E. (“Before Common Era”) and A.D. (“Anno Domini,” in the year of our Lord) with C.E. (“Common Era”) still uses Jesus’ birth to mark time.
To date time in the Old Testament, many writers used the current king or ruler to mark the year that an event occurred. This technique is widespread in the historical and prophetic sections of the Old Testament (e.g. Isa. 6:1). Similarly, though Noah isn’t a king or ruler, Genesis uses his life to mark key moments of the flood story, which helps readers track his age throughout the story.
How long did it take Noah to build the ark?
The time between God announcing that he would destroy the world with a flood and the start of the deluge was 120 years (Gen. 6:3). Knowing this may provide readers with a general timeframe for the ark’s construction.
Though the text reveals that Noah was 600 years old when the flood started, it doesn’t date when God told Noah that a flood was coming (Gen. 6:17) or the patriarch’s subsequent obedience (Gen. 6:22). Did God communicate with Noah at the beginning of the 120 year period, in the middle of it, or toward the end? The text doesn’t say.
One Genesis scholar writes, “We are not told exactly when God’s instructions to Noah were given, though it was obviously sometime after (probably soon after) His prophetic warning that man would have only 120 more years before judgment would come (Genesis 6:3). The work probably was going on throughout most of the century immediately preceding the Flood. 
 The Genesis Record by Henry Morris. p. 183.
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