 The calendars for reckoning the years of kings in Judah and Israel were offset by six months, that of Judah starting in Tishri (in the fall) and that of Israel in Nisan (in the spring).Cross-synchronizations between the two kingdoms therefore often allow narrowing of the beginning and/or ending dates of a king to within a six-month range.For Ahaz, the Scriptural data allow dating the beginning of his coregency with Jotham to some time in the six-month interval beginning of Nisan 1 of 735 BC.