The Question
At the center of this debate is a practical and jurisprudential question that touches every Muslim’s ritual year: how does a lunar month legitimately begin? For most Sunni and Twelver Shia communities, a month opens only when the new crescent (hilal) is actually seen, whether by the naked eye or, in some modern rulings, with the aid of instruments and astronomical confirmation. The Dawoodi Bohra community, by contrast, follows a pre-calculated fixed calendar — an arithmetical or tabular scheme, often called the Misri calendar, inherited from the Fatimid period — in which the length of each month is fixed in advance and the dates of Ramadan, the two Eids, Ashura, and other observances are known and published years ahead of time.
What is disputed is therefore not whether the lunar calendar matters, but whether calculation may substitute for sighting as the authoritative determinant of the month. The stakes are concrete: a calculated date can fall a day before or after the date a sighting committee would announce, which means the community may fast or celebrate Eid on a different day from its neighbours. The question raises issues of scriptural interpretation, the weight of hadith, the scope of an Imam’s or Dai’s authority, and the value placed on advance certainty and worldwide unity.
The Twelver Critique
The Twelver critique, set out for example in Ali Azhar Arastu’s booklet ‘Examining the Ismaili Imams and the Bohras,’ holds that the determination of the month is fixed by revelation and that physical sighting is therefore obligatory. The argument rests first on Quran 2:185, which ties the duty to fast to the one who ‘witnesses’ or is present for the month, and on a large body of hadith — reported across both Sunni and Shia collections — commanding believers to fast when they see the crescent and to break the fast when they see it, and to complete thirty days if it is obscured. Critics note pointedly that a sighting-based report appears in the Da’a’im al-Islam itself, the principal Fatimid legal compendium of al-Qadi al-Nu’man, which they read as evidence that even the foundational Ismaili source presupposes actual observation.
From this premise the critique argues that a purely arithmetical scheme is jurisprudentially unsound: because lunar visibility depends on the moon’s position relative to the sun and the observer’s location, a fixed table cannot guarantee that the crescent is visible on the day it assigns, and may place Eid before the new moon can be seen at all. Over very long spans, critics add, a tabular cycle accumulates a small error against the true lunation and drifts. The conclusion drawn is that the practice departs from what the critic regards as the explicit requirement of scripture and hadith.
The Ismaili-Tayyibi Response
In its own terms, the Dawoodi Bohra tradition presents the fixed calendar not as a miscalculation but as a deliberate, divinely guided institution. On this view, the Fatimid Imams, possessing the authoritative knowledge of the faith, established a calculated calendar so that the ummah could know its sacred dates with certainty and act in unison; the Dai al-Mutlaq, as the Imam’s representative during the period of concealment (satr), continues and safeguards that system. Because the Imam is held to be the rightful interpreter of religion, his sanction of a calculated calendar is itself the legal basis for it, and a sighting report is understood within a layered framework in which the Imam’s directive governs practice.
The tradition further frames the fixed calendar as a positive good rather than a mere convenience: it removes the uncertainty, disputes, and regional fragmentation that can attend sighting, allowing a globally dispersed community to begin Ramadan and celebrate the Eids on a single, predetermined day. Esoteric interpretation (tawil) of the relevant verses and reports is also invoked, so that the outward command to ‘see’ the crescent is read alongside the Imam’s guiding authority rather than against it. Presented this way, the calendar is an intentional, Imam-sanctioned ordering of communal worship grounded in Fatimid precedent.
Scholarly Assessment
Academic historians of Ismailism — among them Farhad Daftary, Wilferd Madelung, and Heinz Halm — document that the use of a calculated lunar calendar is a genuine and long-standing feature of the Fatimid and Tayyibi tradition, attested in the Fatimid period and maintained by the Dawoodi Bohra leadership thereafter; scholarship treats this as an established historical fact about the community’s practice. What scholarship does not adjudicate as settled is the underlying jurisprudential question of whether calculation or sighting is correct, which remains a matter of differing legal schools rather than historical record: most Sunni and Twelver authorities have required sighting, while a minority of Muslim jurists and modern bodies accept astronomical calculation. Claims advanced in polemical literature — for instance the characterization of certain Fatimid-era practices as simple error, or readings of the Da’a’im evidence that assume a single intended meaning — should be marked as contested interpretations rather than neutral facts, since the tradition itself reads the same sources through the lens of the Imam’s interpretive authority.
See also: Scholarly Debates Overview, Daaim Al Islam As A Source, Office Of The Dai Al Mutlaq Debate, Batin Tawil Debate, Fatimid Caliphate