Q: WHAT YEAR DID AHAB BEGIN HIS REIGN IN ISRAEL?
A: IT DEPENDS WHAT CALENDAR YOU ARE USING!
On the Gregorian calendar (the one you might have on your wall) the year was 858 BC.
On the Hebrew calendar, sometimes called the biblical calendar, the year was 3189 AM.
1 Kings 16:28-29 – So Omri slept with his fathers, and was buried in Samaria: and Ahab his son reigned in his stead. And in the thirty and eighth year of Asa king of Judah began Ahab the son of Omri to reign over Israel: and Ahab the son of Omri reigned over Israel in Samaria twenty and two years.