"By means of indirect calculations, one can arrive at such vague dates for the time of his activity as "1000-600 BC." In any case, it seems that Zarathustra must be placed considerably earlier than the Achaemenid Great Kings in the West, such as Cyrus or Darius. Otherwise, however, the veil of timeless Aryan antiquity lies over his life."
January 1, 1970
https://en.wikiquote.org/wiki/Avestan_period