Of course it's the 70 year anniversary of the rebirth of Israel, but the New Moon is the 15th--the evening of the 14th becomes the 15th according to the Jewish calendar. So it's 70 solar years and the beginning of a new lunar month too on that day.
Psalm 90:10 King James Version (KJV)

The days of our years are threescore years and ten; and if by reason of strength they be fourscore years, yet is their strength labour and sorrow; for it is soon cut off, and we fly away.