'Eighth' in the Bible

In the eleventh year [of King Solomon’s reign] in the month of Bul (October-November), that is, the eighth month, the house was finished throughout all its parts and in accordance with all its specifications. So he built it in seven years.

On the eighth (fifteenth) day he sent the people away and they blessed the king. Then they went to their tents joyful and in good spirits because of all the goodness which the Lord had shown to David His servant and Israel His people.

Jeroboam held a feast on the fifteenth day of the eighth month, like the feast which is kept in Judah, and he went up to the altar; he did this in Bethel, sacrificing to the calves which he had made. And he stationed in Bethel the priests of the high places which he had made.

So he went up to the altar which he had made in Bethel on the fifteenth day of the eighth month, in the month which he had devised in his own heart [in defiance of God’s commandments]; and he held a feast for the Israelites and he went up to the altar to burn incense [in defiance of God’s law.]