C. F. Keil and Franz Delitzsch on 2 Kings 15:1

2Ki 15:1

Reign of Azariah (Uzziah) or Judah (cf. 2 Chron 26). - The statement that “in the twenty-seventh year of Jeroboam Azariah began to reign” is at variance with 2Ki 14:2, 2Ki 14:16-17, and 2Ki 14:23. If, for example, Azariah ascended the throne in the fifteenth year of Joash of Israel, and with his twenty-nine years’ reign outlived Joash fifteen years (2Ki 14:2, 2Ki 14:17); if, moreover, Jeroboam followed his father Joash in the fifteenth year of Amaziah (2Ki 14:23), and Amaziah died in the fifteenth year of Jeroboam; Azariah (Uzziah) must have become king in the fifteenth year of Jeroboam, since, according to 2Ki 14:21, the people made him king after the murder of his father, which precludes the supposition of an interregnum. Consequently the datum “in the twenty-seventh year” can only have crept into the text through the confounding of the numerals טו   (15) with כז   (27), and we must therefore read “in the fifteenth year.”