'Seventy Years' in the Bible

Now in that day Tyre will be forgotten for seventy years, like the days of one king. At the end of seventy years it will happen to Tyre as in the prostitute’s song:

It will come to pass at the end of seventy years that the Lord will remember Tyre. Then she will return to her prostitute’s wages and will play the [role of a] prostitute [by trading] with all the kingdoms on the face of the earth.