Did the flood last 40 days or a year? What does the Bible actually say?

When people say "the flood lasted 40 days," they are quoting Genesis 7:12 — and they are right. When they say it lasted a year, they are quoting Genesis 7:11 and 8:14 — and they are also right. The two figures are not contradictions; they measure different phases.

The 40 days: the rain

כִּי֩ לְיָמִ֨ים ע֜וֹד שִׁבְעָ֗ה אָֽנֹכִי֩ מַמְטִ֨יר עַל־ הָאָ֜רֶץ אַרְבָּעִ֣ים י֤וֹם וְאַרְבָּעִים֙ לַ֔יְלָה

"For in seven more days I will send rain upon the earth forty days and forty nights." — Gen 7:4 (MT)

Genesis 7:12 confirms the duration: the rain fell for forty days and forty nights. The verb is H4305 matar in the Hiphil — mamtir, "I will cause rain." God is the named cause. This same Hiphil form appears at Gen 2:5 (YHWH had not yet caused rain), Gen 7:4 (the deluge), and Gen 19:24 (fire on Sodom) — the three canonical threshold-acts of divine matar, bound by one verb.

Forty days measures the rainfall alone, not the flood as a whole.

The 150 days: the waters prevailing

The waters were on the rise long after the rain stopped. Genesis 7:24 — va-yigberu ha-mayim al-ha-aretz hamishim u-meat yom ("and the waters prevailed upon the earth one hundred and fifty days"). Then Genesis 8:3 — after 150 days the waters decreased. The math is built into the narrative's own dates:

From Month 2 to Month 7 is five months; Day 17 to Day 17 is the same day within each month. Five months of thirty days each = 150 days exactly. The 150-day figure in Gen 7:24 and Gen 8:3 is the narrator's own arithmetic, confirmed by the calendar dates he plants in Gen 7:11 and Gen 8:4.

The Hebrew calendar implied here uses 30-day months — a schematic year of 360 days. The symmetry is not coincidence: the narrator gave dates that yield the duration.

The full span: one year and ten days

Six calendar dates anchor the narrative:

From Year 600 / Month 2 / Day 17 (Gen 7:11) to Year 601 / Month 2 / Day 27 (Gen 8:14) is one year and ten days. That is the full time Noah spent in the ark.

The LXX has minor numerical variants but preserves the same overall structure — 150-day symmetry and a year-plus-something total. The Samaritan Pentateuch matches the MT at every chronological figure (SP_Gen.7.11, SP_Gen.8.4, and SP_Gen.8.14 all agree). The MT and SP sing from the same sheet.

Why does the narrator give six dates?

The flood narrative is the most precisely dated section in all of Genesis. Six calendar cues, three explicit durations (7 days, 40 days, 150 days), four seven-day intervals in Panel D (Gen 8:6-12). This is not symbolic number-use — the narrator is giving the reader a calendar, not a code. The chronological density signals that the event is treated as history in real time, with the same precision a court document or a royal chronicle would use.

The full article works through all six dates, the structural chiasm they anchor, and the 150-day calculation in detail in The Flood: Uncreation, Remembrance, Re-creation.