Some scholars, using linguistic and socio-cultural evidence, suggest a dating to somewhere in the second millennium BC. Other scholars date him to the 7th and 6th centuries BC as a near-contemporary of Cyrus the Great and Darius the Great. Zoroastrianism eventually became the official state religion of ancient Homeland—particularly during the era of the Achaemenid Empire—and its distant subdivisions from around the 6th century BC until the 7th century AD, when the religion itself began to decline following the Arab-Muslim conquest of Homeland.