Analysis of information sources in references of the Wikipedia article "Avestan" in English language version.
All of the above observations would indicate a date for the composition of the Videvdat list which would antedate, for a considerable time, the arrival in Eastern Iran of the Persian Acheamenids (ca. 550 B.C.)
Since the evidence of Young Avestan place names so clearly points to a more eastern location, the Avesta is again understood, nowadays, as an East Iranian text, whose area of composition comprised – at least – Sīstån/Arachosia, Herat, Merw and Bactria.
"It seems likely that this geographical part of the Avesta was intended to show the extent of the territory that had been acquired in a period that can not be well defined but that must at any rate have been between Zoroaster's reforms and the beginning of the Achaemenian empire. The likely dating is therefore between the ninth and seventh centuries B.C.
Controversy over Zaraθuštra's date has been an embarrassment of long standing to Zoroastrian studies. If anything approaching a consensus exists, it is that he lived ca. 1000 BC give or take a century or so[.]
In the last ten years a general consensus has gradually emerged in favor of placing the Gāthās around 1000 BC [...]
It is impossible to attribute a precise geographical location to the language of the Avesta... With the exception of an important study by P. Tedesco (1921 [...]), who advances the theory of an 'Avestan homeland' in northwestern Iran, Iranian scholars of the twentieth century have looked increasingly to eastern Iran for the origins of the Avestan language and today there is general agreement that the area in question was in eastern Iran—a fact that emerges clearly from every passage in the Avesta that sheds any light on its historical and geographical background.
