מלכים ב, פרק ט״ו, פסוק ל׳

A violent political coup disrupts the leadership in Israel when Hoshea conspires against the reigning monarch, Pekah, assassinating him and seizing the throne. The timing of this assassination presents a historical puzzle. The record dates the coup to the twentieth year of Jotham, the king of Judah. However, Jotham only ruled for sixteen years. In reality, this violent overthrow took place during the fourth year of the reign of Jotham's son, King Ahaz.

To understand the timeline, one must look at the full twenty-year reign of the assassinated king, Pekah. His rule began during the final year of King Azariah, spanned the entire sixteen-year reign of Jotham, and concluded three years after Jotham's death. Therefore, the year Hoshea took power was indeed the twentieth year since Jotham first took the throne [מצודת דוד].

The decision to avoid dating the event to the fourth year of King Ahaz stems from several possible reasons. The primary approach among commentators suggests a moral motive. Ahaz was known as a wicked ruler. To avoid honoring him while he was alive, the record chose to continue counting the years in honor of his righteous father, Jotham, even though he was already in his grave. Another perspective suggests that this specific method of keeping time was tied to a formal decree established earlier during Jotham's lifetime [רד״ק].

Alternatively, there is a practical, political explanation for this unusual dating. Pekah had been actively warring against Ahaz, seeking to completely dismantle his kingdom and replace him with a different ruler. Because Ahaz's authority was being fiercely contested, the people of that era chose not to calculate the years based on his reign. Instead, they simply continued counting the years from the reign of Jotham, despite his passing [מלבי״ם].