Ever notice when the construction of the 2nd Temple in Jerusalem was supposedly kicked off?
Here's an on-line description:
"The Second Temple was an important Jewish Holy Temple (Hebrew: בֵּית־הַמִּקְדָּשׁ הַשֵּׁנִי, Beit HaMikdash HaSheni) which stood on the Temple Mount in Jerusalem during the Second Temple period, between 516 BCE and 70 CE. According to Judeo-Christian tradition, it replaced Solomon's Temple (the First Temple), which was destroyed by the Neo-Babylonian Empire in 586 BCE, when Jerusalem was conquered and a portion of the population of the Kingdom of Judah was taken into exile in Babylon."
Now, are you looking for 70 years?
Actually, it was Sennecharib that condemned Babylon to a 70 year desolation. And then Esarhaddon came up with a clever way to rescind it. So 70 years had been kind of a middle eastern standard when authorities were severely provoked.
But let's see. What was 70 years before 516 BC?... Did I mention the date?