'Seventy' in the Bible

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?