2 Kings 14:1

In the second year of Joash son of Jehoahaz king of Israel
reigned Amaziah the son of Joash king of Judah.
] As Joash king of Israel began to reign in the thirty seventh of Joash king of Judah, ( 2 Kings 13:10 ) , who reigned forty years, Amaziah must therefore begin his reign in the fourth of Joash king of Israel; this therefore must be understood of his second year after he reigned alone, for he reigned two or three years in his father's lifetime.