“To whom the word of the LORD came in the days of Josiah the son of Amon king of Judah, in the thirteenth year of his reign.”
King James Version (KJV)
1:2 The word - That commission from God that authorized him to his prophetic work, for the space of forty - one years successively in Judea, viz. from the 13th year of Josiah to the 11th year of Zedekiah, besides the time that he prophesied in Egypt. In the days - During his reign. Thirteenth - By which it appears that Jeremiah prophesied the last eighteen years of Josiah's reign; for he reigned thirty - one years, #2Kings 22:1|.