'Seventy Years' in the Bible

This entire land will be a desolation and a waste, and these nations will serve the king of Babylon for seventy years.

"Then when the seventy years have passed, I'll judge the king of Babylon and that nation, declares the LORD, I'll judge the land of the Chaldeans for their iniquity and I'll make it a desolation forever.

"For this is what the LORD says: "When Babylon's seventy years are completed, I'll take note of you and will fulfill my good promises to you by bringing you back to this place.

And the angel of the LORD replied, "LORD of the Heavenly Armies, how long will it be until you show mercy to Jerusalem and to the cities of Judah, with whom you have been angry for these past seventy years?"

"Talk to everyone in the land, as well as to the priests. Ask them, "When you were fasting and mourning during the fifth and seventh months for the past seventy years, were you really fasting for me?