Here's why:
* Ancient Greek pronunciation: The name "Darius" comes from the Ancient Greek name "Dareios." In Ancient Greek, the letter "ι" (iota) was pronounced with a long "i" sound.
* English adaptation: When the name entered English, it retained the long "i" sound.
Therefore, you would pronounce "Darius" as DAY-ree-us, with the "i" in "Darius" sounding like the "i" in "time".