Avestan period

"The Zoroastrians were a colony from Northern India. They had been together for a time with the people whose sacred songs have been preserved to us in the Veda. A schism took place, and the Zoroastrians migrated westward to Arachosia and Persia."

"[If] we use archaeology and history to date the Avesta, we cannot turn around and use the Avesta to date the same archaeological and historical events, and vice versa."

"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."