On May 1, Dr Nazirudin Mohd Nasir, Mufti of Singapore, announced that since the crescent for the month of Shawwal had already set after sunset according to astronomical calculations, May 2 would mark the 30th day of Ramadhan, and Eid would be on May 3.
The announcement caused confusion as neighbouring Malaysia announced that it would be celebrating Eid on May 2, as did a number of other countries around the world. This prompted the Office of the Mufti in Singapore to issue a statement on how the last day of Ramadhan is calculated:
Based on the guidance of the Prophet ﷺ, scholars use two primary criteria, hisab (calculation based on the science of astronomy) and rukyah (رقى, the sighting of the moon) to determine whether the crescent moon is visible.
According to the statement, it is generally extremely difficult in Singapore to see the crescent moon because of predominantly cloudy conditions. Thus, Singapore uses commonly-agreed criteria used by the MABIMS countries (Brunei, Indonesia, Malaysia and Singapore) in determining the sighting of the crescent moon. This methodology is known as imkan ar-rukya.
The imkan ar-rukya criteria was most recently revised in 2021 based on more than 700 data points of crescent sightings from around the world. The new criteria considers two parameters during sunset on the 29th day of the Islamic month – the elevation of the crescent moon (which must exceed three degrees), and the degree of elongation of the sun and the moon (which must exceed 6.4 degrees).
Based on these criteria the crescent moon was not visible in Singapore at sunset on 29 Ramadhan. The Office of the Mufti together with experts in the science of astronomy (الفلك, falak) confirmed this by attempting to conduct a physical sighting of the new moon. This was unsuccessful.
While the religious authorities of other MABIMS countries reported that the crescent moon was visible, they only saw it at selected sites in their own territories.
Although the results differed, all MABIMS countries used the same method of determination which was based on the principles and guidance of the Prophet ﷺ, and their individual results are valid in their respective contexts, with Ramadhan in each country being a maximum of 30 days.
The Office of the Mufti also shared a hadith narrated by Imam Muslim that Mu’awiyah fasted till Friday whereas the rest of the Prophet's ﷺ companions fasted till Saturday based on the differences in sighting the crescent moon in the cities of Sham and Madinah. When asked why they did not simply standardise the fasting period, Ibn ‘Abbas replied that such determination (in following the geographical location of a person) was what had been taught by the Prophet ﷺ, even though it would cause different start and end dates for Ramadhan among Muslims.