In Genesis, on which day did the Flood begin for Noah?

Genesis says Noah's Flood began on the seventeenth day of the second month.

Genesis 7:11 dates the start of the Flood to Noah's six hundredth year, in the second month, on the seventeenth day. It describes the fountains of the deep breaking open and the windows of heaven being opened on that day.

The date belongs to the calendar system used by the biblical narrative, and the text does not identify it with a universally fixed modern calendar date. That distinction matters because later Jewish calendar systems and scholarly reconstructions may handle month names differently.

Readers sometimes confuse this date with other numbers in the story, especially the forty days and forty nights of rain and the 150 days during which the waters prevailed. Those numbers describe later stages of the event rather than its opening date.