Ezra 6:15

6:15 They finished this temple on the third day of the month Adar, which is the sixth ¹  year of the reign of King Darius.

Ezra 10:17

10:17 and on the first day of the first month they finished considering all the men who had married foreign wives.

[6:15]  ¹ sn The sixth year of the reign of Darius would be ca. 516 B.C.