'Forty Years' in the Bible

So the land rested forty years. Then Othniel son of Kenaz died.

So may all your enemies perish, O Yahweh, but those who love him are like the rising sun at its brightest." And the land had rest for forty years.

And Midian was subdued before the {Israelites}, and they did not again lift up their head, and the land rested for forty years in the days of Gideon.

And again, the {Israelites} did evil in the eyes of Yahweh, and Yahweh gave them into the hand of [the] Philistines forty years.