'Thirtieth' in the Bible

Moreover from the time that I was appointed to be their governor in the land of Judah, from the twentieth year even unto the two and thirtieth year of Artaxerxes the king, that is, twelve years, I and my brethren have not eaten the bread of the governor.

But in all this time was not I at Jerusalem: for in the two and thirtieth year of Artaxerxes king of Babylon came I unto the king, and after certain days obtained I leave of the king: