When did Jehoash become king of Israel?

What follows is one scholar’s way of reading this disagreement — a critical-historical view that often concludes the texts genuinely disagree. It draws on the peer-reviewed sources listed below and stands as one position among the answers above, presented for transparency, not as GEBible’s position.

How critical scholarship weighs this: Widely regarded as a genuine contradiction

This summarizes where critical scholarship tends to land on this tension — a report on the field’s center of gravity, not GEBible’s own ruling.

The conflict is internal to a single chapter and surfaces only through arithmetic, which the question's framing makes explicit. 2 Kings 13:10 states directly that Jehoash (Joash) of Israel became king "in the thirty and seventh year of Joash king of Judah." The competing figure is not stated but computed. 2 Kings 13:1 reports that Jehoahaz — Jehoash's father and predecessor on the Israelite throne — became king "in the three and twentieth year of Joash... king of Judah" and reigned seventeen years. Adding the seventeen years of Jehoahaz to his accession in Judah's year 23 yields year 40: Jehoash should therefore have succeeded his father around year 40 of Joash of Judah, not year 37. The discrepancy is three years, and it lives inside the same regnal-framework system the Deuteronomistic Historian used to interlock the two kingdoms' chronologies. (Note the question's first answer cites 13:1, which records Jehoahaz's accession, not Jehoash's; the contradiction is real but indirect, emerging only when 13:1's data are summed against 13:10's stated number.)

The standard conservative resolution is Edwin Thiele's, elaborated by Leslie McFall and Andrew Steinmann: posit an overlap. On this view Jehoash was installed as co-regent alongside his ailing father Jehoahaz around Judah's year 37, then began his sole reign near year 40; the two dates record two milestones — coregency and sole accession — of one reign. The framework is internally coherent and Thiele applies the same coregency mechanism across the many comparable seams in Kings. Coregencies were a genuine ancient Near Eastern institution (the Davidic succession of Solomon during David's lifetime is a biblical instance), so the hypothesis is not impossible in principle.

The critical objection is that the coregency is invoked rather than attested. Nothing in 2 Kings 13 mentions Jehoash ruling beside Jehoahaz; the overlap is reconstructed precisely and only because the numbers fail to add up, and the same move can be deployed wherever a discrepancy appears, which makes it unfalsifiable. Mordechai Cogan and Hayim Tadmor in the Anchor Bible volume classify 13:10 among the synchronisms that resist Thielian reconciliation without ad hoc adjustment, and John Bright and Marvin Sweeney treat the regnal numbers of this period as approximate data drawn from imperfect archival lists rather than a seamless chronology. The textual evidence supports the latter picture: Anneli Aejmelaeus's work on the Old Greek of Samuel–Kings documents that the Septuagint preserves numerous variant regnal and synchronistic figures, indicating that the Hebrew tradition itself was unstable on exactly these numbers. A Historian compiling from divergent king-lists, and not always reconciling them, is the most economical account.

Where the critical reading lands: a numerical contradiction in the received text, derivable by summing the data of 13:1 against the explicit figure of 13:10. It is harmonizable only by positing an unattested coregency the text never mentions; the simpler reading is a redactional inconsistency arising from unreconciled source lists.