When did Noah's flood happen?

In verse 11 God gives the date of the beginning of the flood in relation to the age of Noah, not only the general time, but the exact day, the 17th day of the second month, in Noah's 600th year. The many dates, names and places recorded in scripture are an invitation to anyone to check as he pleases as to the accuracy of the word of God.

From the creation to the flood, when Noah was 600 years old (Gen. 5:3-29; 7:11) 1,656

It is easy to do this, and to make the years from the creation of Adam to the flood to be 1,656. But then the version of the Old Testament in Greek, known as the Septuagint, made about a couple of centuries before the time of our Lord, and, we are told, often quoted by Him, differs from the Hebrew. Adam's age when Seth was born is given as 230, and his subsequent years as 700. The same feature marks the next four patriarchs and also Enoch, so this at once adds 600 years to the calculation.

The most careful research into monuments compared with Berosus (whose chronology the monuments constantly confirm, and other chronological elements and dates) gives about two thousand two hundred and thirty-four years before Christ for the foundation of the first Chaldean kingdom. The common biblical chronology gives for the flood two thousand three hundred and forty-eight… According to the Septuagint chronology, the flood was 3155 B.C.

The hundred and twenty years of which Jehovah spoke was the space of the preparation of the ark and of Noah's preaching. It has nothing to do with the duration of human life, as some have fancied, but of divine patience before "the flood came and took all away."

The tremendous rain lasted for 40 days and 40 nights. The waters prevailed from the 17th day of the 2nd month to the 17th day of the 7th month, when the ark grounded on the mountains of Ararat. On the 1st day of the 10th month the tops of the mountains were seen. On the 1st day of the 1st month of a new year the waters had vanished from the face of the earth. On the 27th day of the 2nd month the earth was sufficiently dry for the occupants of the ark to go forth from it — one year and 10 days having elapsed from the onset.

The judgement of God having exhausted itself, we read that "in the seventh month, on the seventeenth day of the month, the ark came to rest on the mountains of Ararat" (Gen. 8:4). Surely no accident is here. The seventh month became the first at the time of the Exodus (Ex. 12:2); accordingly the ark rested three days after the day appointed for the sacrifice of the Passover lamb, the very day of our Lord's resurrection.