Indonesia is bracing for a potential split in the start of Ramadan 2026, not due to observational challenges, but because of differing criteria used to determine the beginning of the Islamic holy month. The disagreement centers on the application of “local” versus “global” hilal (crescent moon) sighting standards, according to officials at the National Research and Innovation Agency (BRIN).
The Indonesian government, through the Ministry of Religious Affairs, and the majority of Islamic organizations in the country adhere to the “local” hilal criteria, known as MABIMS. This standard requires the hilal to be visible in Indonesia with a minimum height of 3 degrees and an elongation of 6.4 degrees. Muhammadiyah, one of Indonesia’s largest Islamic organizations, employs a “global” hilal criteria. This principle dictates that if the new moon meets visibility criteria anywhere on Earth, and the conjunction occurs before dawn in New Zealand, Ramadan has begun.
Astronomical data from the Meteorology, Climatology, and Geophysics Agency (BMKG) predicts the geosentric conjunction – when the Moon and Sun align – will occur on Tuesday, February 17, 2026, at 7:01 PM Western Indonesian Time (WIB). However, at that time across Indonesia, the hilal will remain below the horizon, with altitudes ranging from -2.41° in Jayapura to -0.93° in West Sumatra. The moon’s age will likewise be negative, indicating the hilal has not yet “born” at sunset.
those following the local hilal criteria are expected to complete the month of Sha’ban with 30 days, placing the first day of Ramadan 1447 H on February 19, 2026. Conversely, proponents of the global hilal criteria point to visibility in locations like Alaska, United States, on February 17th. Because the conjunction occurred before dawn in New Zealand and the hilal was considered “existent” globally, they are likely to commence Ramadan on February 18, 2026, according to BRIN’s Coordinator of Astronomy and the Center for Space Research, Professor Thomas Djamaluddin.
For those awaiting the Indonesian government’s official announcement following the isbat (confirmation) session, observation (rukyatul hilal) will be conducted on the evening of February 18, 2026. At that time, BMKG data indicates the hilal will be significantly more visible, reaching altitudes of 7.62° in Merauke to 10.03° in Sabang, well above the 3° requirement. Elongation will range from 10.7° to 12.21° (exceeding the 6.4° threshold), and the moon’s age will be 20 to 23 hours.
Despite the clarity provided by scientific calculations (hisab), the Indonesian government will still hold the isbat session on February 17, 2026. This session serves as a formal confirmation, reconciling mathematical calculations with observational data. Professor Djamaluddin emphasized that the purpose of the scientific data is not to create conflict, but to provide an objective understanding of the reasons for the potential differences. “Astronomically, there is no erroneous data; the differences arise solely from the different criteria believed,” he stated.
Consumer insights from YouGov, covering Indonesia, Malaysia, Saudi Arabia, Türkiye and the UAE, indicate a heightened focus on religious observance during Ramadan 2026, but do not address the potential divergence in start dates. The government has also set school learning policy for Ramadan 2026, but details of that policy were not available.