This Bible contradiction is from the Skeptic's Annotated Bible.

Verses

Seven days before the flood began.

Genesis 7:7-10 View context

And Noah went in, and his sons, and his wife, and his sons' wives with him, into the ark, because of the waters of the flood.

Of clean beasts, and of beasts that [are] not clean, and of fowls, and of every thing that creepeth upon the earth,

There went in two and two unto Noah into the ark, the male and the female, as God had commanded Noah.

And it came to pass after seven days, that the waters of the flood were upon the earth.

The day that the flood began.

Genesis 7:11-13 View context

In the six hundredth year of Noah's life, in the second month, the seventeenth day of the month, the same day were all the fountains of the great deep broken up, and the windows of heaven were opened.

And the rain was upon the earth forty days and forty nights.

In the selfsame day entered Noah, and Shem, and Ham, and Japheth, the sons of Noah, and Noah's wife, and the three wives of his sons with them, into the ark;