Ezra 4:5

(5) And hired counsellors against them.—They adopted a systematic course of employing paid agents at the court: continued for eight years, till B.C. 529. Cambyses, his son, succeeded Cyrus; he died B.C. 522; then followed the pseudo-Smerdis, a usurper, whose short reign Darius did not reckon, but dated his own reign from B.C. 522. A comparison of dates shows that this was the first Darius, the son of Hystaspes.