Albert Barnes Commentary 2 Kings 22:3

"And it came to pass in the eighteenth year of king Josiah, that the king sent Shaphan, the son of Azaliah the son of Meshullam, the scribe, to the house of Jehovah, saying," — 2 Kings 22:3 (ASV)

In the eighteenth year - This is the date of the finding of the Book of the Law and of the Passover (see the marginal reference and 2 Kings 23:23), but it does not apply to all the various reforms of Josiah as described in 2 Kings 23:4–20. The true chronology of Josiah’s reign is learned from 2 Chronicles 34:3–8 and 2 Chronicles 35:1. From these passages, it appears that most of his reforms preceded the finding of the Book of the Law. He began them in the 12th year of his reign, at the age of 20, and had accomplished all, or most of them, by his 18th year, when the Book of the Law was found.

Shaphan is mentioned frequently by Jeremiah. He was the father of Ahikam, Jeremiah’s friend and protector at the court of Jehoiakim (Jeremiah 26:24), and the grandfather of Gedaliah, who was made governor of Judea by the Babylonians after the destruction of Jerusalem (2 Kings 25:22). Several of his other sons and grandsons were in favor with the later Jewish kings (Jeremiah 29:3; 36:10-12, 25; Ezekiel 8:11). Shaphan’s office was one of great importance, involving very confidential relations with the king (1 Kings 4:3).