In 735 BC, during the seventeenth year of King Pekah's reign, Ahaz began to rule. He had been co-ruler for eleven years, but now he officially became king. This marked his transition from being under his father Jotham, who ruled from 743 to 735 BC, to ruling in his place from 735 to 732 BC. Ahaz likely had his official accession ceremony after his father's death in 732 BC. The author of Kings counts Ahaz's reign as lasting sixteen years, from 731 BC (the year after his father died) to 715 BC. See also study note on 2 Kings 17:1.