Bible Verses About Years: Length of, during the patriarchal age

On the seventeenth day of the second month of the 600th year of Noach’s life all the fountains of the great deep were broken up, and the windows of the sky were opened.

The water held power over the earth for 150 days.

and the water came back from completely covering the earth. It was after 150 days that the water went down.

By the first day of the first month of the 601st year the water had dried up from off the earth; so Noach removed the covering of the ark and looked; and, yes, the surface of the ground was dry.