Scientific Reasons Behind Muhammadiyah's Decision to Set 1 Ramadan 1447 H on 18 February 2026, Using a Different Method from the Government
Jakarta, VIVA – The determination of the start of Ramadan 1447 Hijriah has once again produced differences in Indonesia. Muhammadiyah has set 1 Ramadan as falling on Wednesday, 18 February 2026, whilst the government is expected to declare it one day later.
Behind this difference lies a fundamental change in the method of determining the Islamic calendar now adopted by Muhammadiyah. Indonesia's second-largest Islamic organisation has officially adopted the Single Global Hijri Calendar (Kalender Hijriah Global Tunggal/KHGT), a global Islamic calendar concept that emphasises unity of time for Muslims worldwide.
Muhammadiyah's Islamic astronomy expert, Arwin Juli Rakhmadi Butar-Butar, as quoted on Muhammadiyah's official website, explained that the 18 February decision was not made hastily but rather resulted from the consistent application of astronomical and jurisprudential parameters within the KHGT framework.
According to him, Muhammadiyah established 1 Ramadan 1447 H on 18 February 2026 as set out in the Central Leadership of Muhammadiyah's Proclamation Number 2/MLM/I.0/E/2025 and the explanation from the Tarjih and Tajdid Council. This determination also marks the official adoption of the KHGT, replacing the wujudul hilal method that Muhammadiyah had used for decades.
Astronomically, the start of a Hijri month is determined by the conjunction event, or ijtimak. For Ramadan 1447 H, the ijtimak occurs on Tuesday, 17 February 2026, at 12:01 UTC or 19:01 Western Indonesian Time (WIB). This event marks the end of the previous lunar cycle and the beginning of a new lunar phase.
Under the KHGT, a new month is declared to have begun if, following the ijtimak, the position of the crescent moon (hilal) meets the minimum parameters of 5 degrees altitude and 8 degrees elongation anywhere on the Earth's surface. According to Arwin, these parameters were met on 17 February 2026 in Alaska, United States, with a hilal altitude of 5 degrees 23 minutes and elongation exceeding 8 degrees.
As the hilal astronomically met the global criteria after sunset in that region, Muhammadiyah determined the following day, 18 February 2026, as 1 Ramadan globally.
Meanwhile, conditions differ in Indonesia. After sunset on the same day, the position of the hilal remains below the horizon and therefore does not meet the government's criteria. The criteria used by the government through the Ministry of Religious Affairs refer to the MABIMS standard, requiring a minimum hilal altitude of 3 degrees and elongation of 6.4 degrees within Indonesian territory.
As these parameters have not yet been met locally, the start of Ramadan in Indonesia is likely to be set as Thursday, 19 February 2026, through the rukyat observation mechanism and the isbat session.
Behind this difference lies a fundamental change in the method of determining the Islamic calendar now adopted by Muhammadiyah. Indonesia's second-largest Islamic organisation has officially adopted the Single Global Hijri Calendar (Kalender Hijriah Global Tunggal/KHGT), a global Islamic calendar concept that emphasises unity of time for Muslims worldwide.
Muhammadiyah's Islamic astronomy expert, Arwin Juli Rakhmadi Butar-Butar, as quoted on Muhammadiyah's official website, explained that the 18 February decision was not made hastily but rather resulted from the consistent application of astronomical and jurisprudential parameters within the KHGT framework.
According to him, Muhammadiyah established 1 Ramadan 1447 H on 18 February 2026 as set out in the Central Leadership of Muhammadiyah's Proclamation Number 2/MLM/I.0/E/2025 and the explanation from the Tarjih and Tajdid Council. This determination also marks the official adoption of the KHGT, replacing the wujudul hilal method that Muhammadiyah had used for decades.
Astronomically, the start of a Hijri month is determined by the conjunction event, or ijtimak. For Ramadan 1447 H, the ijtimak occurs on Tuesday, 17 February 2026, at 12:01 UTC or 19:01 Western Indonesian Time (WIB). This event marks the end of the previous lunar cycle and the beginning of a new lunar phase.
Under the KHGT, a new month is declared to have begun if, following the ijtimak, the position of the crescent moon (hilal) meets the minimum parameters of 5 degrees altitude and 8 degrees elongation anywhere on the Earth's surface. According to Arwin, these parameters were met on 17 February 2026 in Alaska, United States, with a hilal altitude of 5 degrees 23 minutes and elongation exceeding 8 degrees.
As the hilal astronomically met the global criteria after sunset in that region, Muhammadiyah determined the following day, 18 February 2026, as 1 Ramadan globally.
Meanwhile, conditions differ in Indonesia. After sunset on the same day, the position of the hilal remains below the horizon and therefore does not meet the government's criteria. The criteria used by the government through the Ministry of Religious Affairs refer to the MABIMS standard, requiring a minimum hilal altitude of 3 degrees and elongation of 6.4 degrees within Indonesian territory.
As these parameters have not yet been met locally, the start of Ramadan in Indonesia is likely to be set as Thursday, 19 February 2026, through the rukyat observation mechanism and the isbat session.