1 Kings 15:28

Third year of Asa. Nadab began his reign in the second year of Asa (v. 25) and was slain by Baasha in the third year of Asa, after a reign of two years (v. 25). This was possible because Nadab’s reign was reckoned according to a system in which Jeroboam’s last year was also reckoned as Nadab’s first year, and any part of the following regnal year in which Nadab reigned was considered his second year. Seeing he reigned during parts of the two regnal years, he would be said to reign two years (see p. 137; also PK 109).