'Seventy' 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 song of the harlot:

It will come about at the end of seventy years that the Lord will visit Tyre. Then she will go back to her harlot’s wages and will play the harlot with all the kingdoms on the face of the earth.