'Seventy Years' in the Bible

The angel of the Lord then asked, "Lord who rules over all, how long before you have compassion on Jerusalem and the other cities of Judah which you have been so angry with for these seventy years?"

"Speak to all the people and priests of the land as follows: 'When you fasted and lamented in the fifth and seventh months through all these seventy years, did you truly fast for me -- for me, indeed?