This article examines the Quranic expression of 309 years in Sūrah al-Kahf (18:25), which states “three hundred years, and add nine” rather than simply “three hundred and nine years.” The analysis explores the two primary interpretations among classical Quranic exegetes (mufassirūn): the dominant view, which posits that this expression reflects both solar (300 years) and lunar (309 years) calendar calculations, which each related to certain audiences of the Quranic passage, and the alternative view, which suggests that the expression relates the People of the Book’s conjecture and disagreement regarding this duration, serving as a rebuke for delving into matters beyond their knowledge. The paper lays out the classical debate regarding the alternate view, examines the re-engagement of this debate by contemporary Muslim writers, and traces the connection of that engagement with Western academics in the field of history, in dialogue with Muslim historical scholarship.
