What year did Josiah find the Book of Deuteronomy and implement the Deuteronomistic Reforms?

A:

Josiah began his reign in 649 BCE. In the eighteenth year, or about 631 BCE, he ordered renovations for the temple in Jerusalem, and it was shortly after that the Book of Deuteronomy, or perhaps an early version of it, was supposedly found in the temple. Scholars believe the priests placed it there, then found it, in order to prove its antiquity. A very similar example of this deception is reported in the Book of Jeremiah some years later.

King Josiah made a public show of emotion at finding laws that were not being followed, and began the reforms he is noted for.