In the twelfth year of Joram the son of Ahab king of Israel did Ahaziah the son of Jehoram king of Judah begin to reign. 2 Kings 8:25
And in the eleventh year of Joram the son of Ahab began Ahaziah to reign. 2 Kings 9:29
Note for 2 Kings 9:29 in The New Oxford Annotated Bible: This verse may be a correction of 8.25.