Unifying the Hijri Calendar: A Fiqh al-Siyāsa Model for Legal Authority and Certainty

The unification of the Hijri calendar remains a major legal challenge because Muslim states and religious organizations continue to declare different dates for important religious months despite adopting similar visibility criteria. Existing studies primarily frame this issue as an astronomical debate, leaving the question of legal authority insufficiently explored. This article examines how Islamic legal theory distinguishes ritual worship from civil administration in determining the Hijri calendar. Utilizing normative legal research, this analysis employs doctrinal and comparative approaches to examine classical fiqh, regulatory documents, and contemporary scholarship through the maqāṣid al-sharī‘a framework. The study proposes a Pragmatic Bifurcation Model that preserves local sighting authority for ritual worship while requiring a unified calculated calendar for civil affairs under fiqh al-siyāsa. Analysis of Indonesia's implementation reveals that legal certainty primarily depends on effective state authority rather than precise calculations. The findings suggest that strengthening governmental authority while maintaining doctrinal pluralism offers a more workable path toward Hijri calendar harmonization.