1 Kings 16:23

16:23 In the thirty-first year of Asa king of Judah began Omri to reign over Israel, [and reigned] twelve years: six years reigned he in Tirzah.
-World English Bible

Other Translation

16:23 In the thirty and first year of Asa king of Judah began Omri to reign over Israel, twelve years: six years reigned he in Tirzah.
-King James Version