Ancient Persian refers to the culture and civilization of the ancient Iranian peoples, which spanned from the 6th century BC to the 7th century AD. Zoroaster was an ancient Iranian prophet who founded the religion of Zoroastrianism in the 6th century BC. The Medes were an ancient Iranian people who established an empire in the 7th century BC. Xerxes I was a king of the Achaemenid Empire, an ancient Iranian empire that ruled from 559 BC to 330 BC. Satraps were governors of provinces in the Achaemenid Empire. Omar was a caliph of the Umayyad dynasty, an Islamic dynasty that ruled from 661 AD to 750 AD. Satraps were also governors of provinces in the Sasanian Empire, an ancient Iranian empire that ruled from 224 AD to 651 AD. IRAN is the modern-day name for the region that was once the Achaemenid and Sasanian Empires.