MUHAMMADIYAH.OR.ID, MAKASSAR — In Islam, determining prayer times and the direction of the Qibla has relied on astronomical calculations, known as hisab. These calculations are widely accepted by scholars and are seen as accurate tools to support daily worship.
However, when it comes to determining the start of Ramadan and Shawwal, opinions often differ. Speaking at the National Tarjih Cadre Training in Makassar on Friday, May 30, the Chairperson of the Muhammadiyah Provincial Board of South Sulawesi, Ambo Asse, explained the root of this ongoing debate.
The disagreement centers on two main approaches to calculating the Islamic lunar calendar: hisab urfi and hisab hakiki. Each method reflects a different understanding of the moon’s movement.
Hisab urfi is a simplified method that doesn’t rely on direct observation of the moon. Instead, it follows a fixed pattern based on average lunar cycles, assigning each month a set number of days. For example, Ramadan—being the ninth month—is always considered 30 days long using this method. However, in reality, as observed from the sky, Ramadan may only last 29 days. This means the hisab urfi calendar doesn’t always match the actual appearance of the new moon, or hilal. Sometimes, the calendar is ahead of, behind, or in sync with the moon’s actual cycle.
On the other hand, hisab hakiki is based on the moon’s actual position in the sky. It uses precise astronomical calculations to determine the start and end of each lunar month. While this method is more accurate in theory, it introduces new challenges due to the variety of criteria used to decide when the new month begins.
Ambo Asse outlined three commonly used criteria in hisab hakiki. The first is ijtima’ before dawn, which considers the new month to start if the conjunction of the sun and moon happens before dawn. If the conjunction occurs after dawn, the current month continues until the next day.
The second is ijtima’ before sunset, which follows the idea that the day begins at sunset. If the conjunction takes place before sunset, then the new month starts that evening. If it occurs afterward, the current month continues for one more day. This method does not consider whether the moon is visible.
The third approach is imkan rukyat, or the visibility of the crescent moon. In this method, the new month only begins if the moon is visible to the naked eye on the evening of the 29th day of the current month. However, scholars have not agreed on the minimum height the moon should be to qualify as visible, which makes this method less consistent.
Looking ahead to the Islamic year 1447 AH, Ambo Asse said that Muhammadiyah is planning to adopt the imkan rukyat method as part of its move toward a Unified Global Hijri Calendar. Under this plan, the new month will begin when the moon is at least 5 degrees above the horizon and has an elongation of 8 degrees, regardless of the observer’s location on Earth.
“This step reflects an effort to unite Muslims around the world under a unified calendar, while also integrating advancements in astronomical science with religious traditions,” said Ambo Asse.
