Albert Barnes Commentary 2 Kings 15:8

"In the thirty and eighth year of Azariah king of Judah did Zechariah the son of Jeroboam reign over Israel in Samaria six months." — 2 Kings 15:8 (ASV)

In the thirty-eighth year — This should rather be read as the 27th year of Azariah, according to the chronology in 2 Kings 14:23 and 2 Kings 15:2. Some suppose there was an interregnum between Jeroboam and Zachariah, which, however, is very improbable.