'Eighth' in the Bible

In the eleventh year, in the month Bul (the eighth month) the temple was completed in accordance with all its specifications and blueprints. It took seven years to build.

Jeroboam inaugurated a festival on the fifteenth day of the eighth month, like the festival celebrated in Judah. On the altar in Bethel he offered sacrifices to the calves he had made. In Bethel he also appointed priests for the high places he had made.

On the fifteenth day of the eighth month (a date he had arbitrarily chosen) Jeroboam offered sacrifices on the altar he had made in Bethel. He inaugurated a festival for the Israelites and went up to the altar to offer sacrifices.