SINGAPORE - Some Muslims in Singapore have been wondering why Hari Raya Puasa here falls on Tuesday (May 3) when neighbouring countries Malaysia, Indonesia and Brunei are celebrating the festival on Monday (May 2).

Singapore Mufti Nazirudin Mohd Nasir, the Republic's top Islamic leader, announced on Sunday (May 1) night that Muslims here will celebrate Hari Raya Puasa, also known as Hari Raya Aidilfitri, on Tuesday.

This is because according to astronomical calculations, the crescent moon for the Islamic month of Syawal, which follows Ramadan, did not appear in the evening after sunset on Sunday.

The crescent moon - which traditionally marks the start of a new month - could not be seen either, the Mufti added.

Nevertheless, questions about the discrepancy continued to be asked on social media, given that the rest of the region is marking the festival a day earlier.

In a statement on Monday morning, the Office of the Mufti explained that in this region, differences in the start of the Hijri, or Islamic calendar, have occurred very frequently in the past - as recently as 2014, 2015, 2016, 2017 and 2021 - and may well occur again in future.

Thus, in 2022, not all countries in the world, including Muslim-majority countries, celebrate Ramadan and Aidilfitri on the same dates.

"Indeed, the crescent moon has also not been sighted in a few other countries, and as a consequence, they will be celebrating Aidilfitri on Tuesday, May 3, like Singapore," the statement said.

Bangladesh, India and Pakistan are among the countries celebrating the festival on Tuesday.

Added the statement: "For as long as we hold true to the principles of our faith and the guidance of the Prophet Muhammad, differences in the determination of the Islamic calendar is something which is neither unexpected nor alarming."

The Office of the Mufti explained that Muslims are taught that if the moon is obscured, they are to regard Ramadan as having 30 days.

According to the Islamic calendar, which is lunar, some months can last 29 days and others 30 days.

Scholars have used two primary criteria - calculation based on astronomy, and the sighting of the moon - to determine whether the crescent moon is visible.

However, in Singapore, it is generally extremely difficult for the crescent moon to be visible because of climatic conditions, which are often cloudy.

Singapore therefore uses the commonly agreed upon criteria used by four regional countries in MABIMS, an informal gathering of religious ministers of Brunei, Indonesia, Malaysia and Singapore, in determining the sighting of the crescent moon.

These criteria have been reviewed and refined by the four countries since 2017, and revised in 2021, based on more than 700 data points of crescent sightings from around the world.

The new criteria consider two parameters during sunset on the 29th day of the 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 Ramadan," the statement said.

"For confirmation, the Office of the Mufti together with experts in the science of falak (astronomy) attempted to conduct a physical sighting of the crescent moon, which was unsuccessful - that is, the new moon was not visible.

During the sighting, it was also clear that the western horizon was overcast with clouds," it added.

The statement noted that the religious authorities of the other MABIMS countries reported that the crescent moon was visible in their sightings only at certain sites in their own territories.

"Their individual results are valid in their respective contexts," it said.

The statement added that early Muslim chroniclers also acknowledged differences in determining the start or end of Ramadan in different cities, based on differences in sighting the crescent moon.

It noted that this year, Ramadan would last 30 days for the Singapore Muslim community, which should continue to fast on Monday.