In the Genesis account, on what date did the Flood begin for Noah's Ark?

In the Genesis account, the Flood began on the seventeenth day of the second month for Noah’s Ark.

Genesis 7:11 dates the beginning of the cataclysm to the seventeenth day of the second month in Noah’s six-hundredth year. The passage says that the fountains of the great deep burst open and the windows of heaven were opened. Genesis 7:12 then says rain fell for forty days and forty nights.

The biblical narrative uses a month-and-day calendar rather than naming a modern month. This means the date cannot be converted into a single modern calendar date without knowing which calendar system and month lengths are intended. The text also distinguishes the start of the Flood from later dates marking the ark’s resting and the appearance of dry land.

Readers sometimes combine the forty days of rain with the entire duration of the Flood. Genesis presents several separate time markers: rain for forty days, waters prevailing for 150 days, and the ark eventually coming to rest in the seventh month.