'Seventy' in the Bible

Then the angel of the Lord said, “O Lord of hosts, how long will You have no compassion for Jerusalem and the cities of Judah, with which You have been indignant these seventy years?”

“Say to all the people of the land and to the priests, ‘When you fasted and mourned in the fifth and seventh months these seventy years, was it actually for Me that you fasted?