MUHAMMADIYAH.OR.ID, YOGYAKARTA – A member of the Muhammadiyah Council for Religious Opinion Tajdid Arwin Juli Rakhmadi Butar-Butar addressed 33 critical points raised about the proposed Unified Global Hijri Calendar during a national forum held in Yogyakarta on Saturday, April 19. His explanation aimed to clarify key concerns, ranging from who should have the authority to set a global calendar to how the calendar’s technical aspects should be verified.
One major concern was the need for an official global body to decide on the Hijri calendar. Some critics referred to Caliph Umar ibn Khattab, who formalized the original Hijri calendar, as a precedent. However, Arwin disagreed with the idea that a central authority is necessary today.
“I disagree with the idea of a central authority in the global calendar concept because it is difficult to determine who holds the highest authority in the world today,” said Arwin.
Arwin questioned suggestions to assign this role to the Organization of Islamic Cooperation (OIC), warning that political interests could affect its credibility.
“If the authority loses its legitimacy, what happens to the calendar?” he asked.
Instead, Arwin proposed a more flexible approach. “Countries that want to adopt the unified global hijri calendar can do so. Those who need more time to review it are welcome, and those who disagree can follow their own system,” he explained.
Another issue discussed was the technical standard of the unified global hijri calendar, which sets a minimum moon height of five degrees and an elongation angle of eight degrees as the criteria for the new month. Arwin acknowledged that many Muslims still rely on physical moon sightings and said these criteria should be verified with real-world observation.
“This kind of verification can strengthen support for the unified global hijri calendar, especially in the concept of a global sighting zone, where a sighting in one place can apply worldwide,” he explained.
Arwin stressed that this process should combine both calculation and actual observation to ensure accuracy. He gave an example from Africa where the crescent moon did not meet the unified global hijri criteria, but in Hawaii, it did.
“Should Hawaii start the new month, wait until 30 days are completed, or delay it? These are the kinds of questions we need to explore further,” he said.
He also noted cases where the moon was seen at a height just below five degrees—such as 4.5 degrees—but could still be confirmed with scientific evidence. “This is an important point for the unified global hijri calendar implementation,” he added.
Some in Indonesia have suggested unifying local calendars first before moving on to a global version. However, Arwin argued that starting with a global approach would be more efficient.
“If we unify the local calendar first and then propose it globally but get rejected, we would have to revise everything. That would waste time,” he said. He admitted that both approaches have strengths and weaknesses and that a balanced solution is needed.
Another question often raised is why the unified global hijri calendar uses midnight (00:00) as the starting point for the date, which some see as a solar-based system. Arwin explained that this is the most logical and practical choice to ensure a single date applies across all time zones.
“If we use the time of dawn instead, the unified global hijri calendar wouldn’t work consistently around the world,” he stated.
He also responded to criticism about the inclusion of the word “America” in one of the unified global hijri calendar clauses, which sparked objections from some groups in Medan.
“Some have suggested that we avoid mentioning specific regions like America and use geographic descriptions instead, to avoid controversy,” he said.
Arwin emphasized that all these criticisms are valuable for improving the unified global hijri calendar and making it more acceptable globally.
“If we can verify the 5-8 criteria through actual observation, it will make the unified global hijri calendar easier to implement. We also need to come up with solutions for special cases, like when the moon’s height falls below the standard or visibility differs between regions,” said Arwin.
A full version of Arwin’s response is available in the Indonesian language through the following link.
