'Seventy' in the Bible

And the angel of Jehovah answered and said, Jehovah of hosts, how long wilt thou not have mercy on Jerusalem and on the cities of Judah, against which thou hast had indignation these seventy years?

Speak unto all the people of the land, and to the priests, saying, When ye fasted and mourned in the fifth and in the seventh month, even those seventy years, did ye really fast unto me, even unto me?