'Year' in the Bible

In the eighth month, in the second year of Darius, came the word of the LORD unto Zechariah, the son of Berechiah, the son of Iddo the prophet, saying,

Upon the four and twentieth day of the eleventh month, which is the month Sebat, in the second year of Darius, came the word of the LORD unto Zechariah, the son of Berechiah, the son of Iddo the prophet, saying,

And it came to pass in the fourth year of king Darius, that the word of the LORD came unto Zechariah in the fourth day of the ninth month, even in Chisleu;

And it shall come to pass, that every one that is left of all the nations which came against Jerusalem shall even go up from year to year to worship the King, the LORD of hosts, and to keep the feast of tabernacles.