Zoroaster and the problem of several clocks.
Separate a traditional founder, a textual layer, later witnesses, and the religion’s subsequent history.
Begin with the texts
Iranica’s entry on Zoroaster in the Avesta is a guide to textual testimony. A tradition about a founder and the date assigned to a text are related questions, but they are not interchangeable. Encyclopaedia Iranica ↗
Keep several dates visible
Distinguish proposed composition, surviving manuscript dates, and later religious reception. An exact-looking date should not hide the competing chronology models in the research record. Encyclopaedia Iranica ↗
Follow the later history separately
The historical review of Zoroastrianism after the Arab conquest supplies another chronological layer. Later survival or reinterpretation does not independently establish an origin date. Encyclopaedia Iranica ↗