The Unified Global Hijri Calendar represents Muhammadiyah’s contribution to establishing a unified, scientific Hijri calendar that can be embraced by Muslims worldwide. Its primary aim is to address the recurring inconsistencies in determining the beginning of Hijri months, particularly Ramadan, Shawwal, and Dhu al-Hijjah, across various countries and even among different communities within the same region. By proposing a calendar system that is technically accurate, astronomically synchronized, scientifically verifiable, and rooted in Islamic principles, Muhammadiyah seeks to foster greater global unity among Muslims.
The Unified Global Hijri Calendar also embodies Muhammadiyah’s broader effort to modernize the Hijri calendar as a fundamental institution of Islamic civilization, particularly in the context of an increasingly interconnected global Muslim society. This initiative emerged from the need to resolve challenges related to time standardization, calendar accuracy, and global synchronization in religious observances.
Importantly, this initiative draws upon the rich intellectual heritage of Islamic astronomy. Muslim scholars have long contributed to the development of astronomical knowledge. Al-Battani (858–929 CE), for instance, refined Ptolemaic data and produced influential astronomical tables; Al-Biruni (973–1048 CE) employed experimental and observational methods to measure time, seasons, and celestial movements; and Nasir al-Din al-Tusi (1201–1274 CE) established the Maragha Observatory and proposed planetary motion models that later influenced Copernican theory.
Although precise hisab methods have existed since the classical period, their global application has been limited due to particularly the view in some schools of thought that rukyat (visual moon sighting) is the only valid method. The current initiative represents a continuation of the scientific spirit of classical Muslim scholars, adapting their legacy to the technological realities of the modern era.
Since its introduction, the unified global Hijri calendar has generated public interest as well as misunderstanding. One recurring concern is the perceived impossibility of global calendar standardization. While such skepticism is understandable, current astronomical tools now allow the positions of the moon and sun to be calculated with millisecond precision and synchronized with Coordinated Universal Time (UTC). Technologically, there is no barrier to implementing a unified Hijri calendar. However, realizing this vision requires sustained dialogue and collaboration among scholars, governments, and Islamic organizations across the world. The greatest challenge lies not in technical feasibility, but in fostering a collective awareness of symbolic unity in worship.
Muhammadiyah officially begins the implementation of the Unified Global Hijri Calendar on Muharram 1, 1447 AH. Thus, the book explaining the Unified Global Hijri Calendar has been prepared as a reference for Muhammadiyah members and other interested readers. It aims to elucidate the conceptual underpinnings and objectives of this significant initiative.
The book of the Unified Global Hijri Calendar can be downloaded here.
