'Days' in the Bible

And the Lord made ready a great fish to take Jonah into its mouth; and Jonah was inside the fish for three days and three nights.

So Jonah got up and went to Nineveh as the Lord had said. Now Nineveh was a very great town, three days' journey from end to end.

And Jonah first of all went a day's journey into the town, and crying out said, In forty days destruction will overtake Nineveh.