The Beginning of the Flood

The date is given with rare precision: «In the six hundredth year of Noach's life, in the second month, on the seventeenth day of the month — on that day all the fountains of the great deep burst open, and the windows of heaven were opened.» Water came from below and above at once. Rain fell forty days and forty nights; the waters rose for a hundred and fifty days, fifteen cubits above the highest mountains, and everything on dry land in whose nostrils was the breath of life died.

Noach was told to enter the ark and given seven more days. The Torah notes that «the Lord shut him in» — a human hand did not close the door. Noach was exactly six hundred: born in 1056, so the year is 1656.

Which month is «the second» is disputed: R. Eliezer counts from Tishrei, making it Marcheshvan; R. Yehoshua counts from Nisan, making it Iyar. This timeline follows the first view: 17 Cheshvan. The Flood lasts a full solar year, until a dove returns with a plucked olive leaf.