'Twentieth' in the Bible

The words of Nehemiah son of Hacaliah. It happened in the month of Kislev, in the twentieth year, that I myself was in the citadel in Susa,

It happened in the month of Nisan, in the twentieth year of King Artaxerxes, when wine was before him, I carried the wine and gave it to the king. And I had never been sad before the king.

Moreover, from the appointed day I was made their governor in the land of Judah, from the twentieth year until the thirty-second year of King Artaxerxes--twelve years. My brothers and I did not eat the food [allowance] of the governor.