Home community How the date for Hari Raya is determined: Where science and faith meet

How the date for Hari Raya is determined: Where science and faith meet

How the date for Hari Raya is determined: Where science and faith meet

SINGAPORE – Earlier in April, the Abu Dhabi-based International Astronomical Centre announced that the crescent moon marking the end of Ramadan would be sighted on April 20, making the next day Hari Raya Puasa.

Subsequently, Malaysia’s Fatwa Committee said it would discuss the centre’s prediction, with Federal Territories Mufti Luqman Abdullah stating on April 13 that the country’s celebrations will be determined by its own astronomical calculations or the sighting of the new moon following sunset on Thursday.

This year, Singapore will celebrate Hari Raya Puasa on Saturday, April 22. 

With Hari Raya Puasa fast approaching, The Straits Times looks at the science behind how such dates are calculated, as well as other facts relating to Ramadan and Hari Raya.

Q: Why do Muslims fast during Ramadan, and what happens to your body when you fast?

A: Fasting in the day, from dawn to sunset, during Ramadan is one of the five pillars of Islam, with all able-bodied adult Muslims expected to observe the fast.

The practice aims to restrain desires and inculcate righteousness.

Certain categories of people – such as pregnant or breastfeeding women, as well as those with chronic illnesses and prepubescent children – are exempt from fasting.

In Singapore, Muslims typically fast for about 13 hours each day. Research suggests fasting for this amount of time can help the body turn its fat stores into energy, thus resulting in weight loss.

A study published in the Journal of Public Health in 2012 suggested that those observing Ramadan can lose about 1kg over the month.

Several studies have shown other benefits associated with fasting, such as helping to lower cholesterol, lower blood sugar levels and preventing inflammation.

Hypertension specialist Adrian Mondry said those with hypertension or cardiovascular disease should consult their doctors before deciding if they can fast during Ramadan.

Those with well-managed cardiovascular diseases should not face serious health issues if they fast, he added.

However, said Dr Mondry, the medical director of Kaizen Medical Clinic at Mount Elizabeth Novena Specialist Centre, those with myocardial infarction, decompensated heart failure, or those who have uncontrolled hypertension with multiple medications, are advised not to fast.

Q: Why do Muslims eat dates when they break their fasts? What are the benefits associated with the fruit?

A: Many eat dates to break their fasts as this was the practice of Prophet Muhammad.

Dates help restore energy after a day of fasting as they contain glucose, fructose and sucrose, as well as fibre, potassium and vitamin A.

Despite their sweetness, the low glycaemic index of dates means they will not cause your blood sugar levels to spike. 

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Q: Why does the date for Hari Raya Puasa change every year? How is this date determined?

A: Hari Raya Puasa is celebrated on the first day of Syawal, the 10th month of the Islamic calendar. As Muslims follow a lunar calendar, each year is only 355 or 354 days. Therefore, the dates move forward about 11 days each year on the Gregorian calendar.

While Muslims in many places still rely on observation of the new moon to mark the beginning of both Ramadan and Syawal, the Islamic Religious Council of Singapore (Muis) has used hisab, or astronomical calculation, to determine the beginning of the Islamic months since 1974.

This is because factors such as cloud cover in Singapore – where it rains an average of 167 days of the year – as well as light pollution prevent the moon from being seen in its earliest stages.

Since 2017, the criteria for the calculation, based on 737 observations from around the world, include two parameters during sunset on the 29th day of Ramadan – the elevation of the crescent moon, which must exceed 3 degrees, and the degree of elongation of the sun and the moon, which must exceed 6.4 degrees.

These are spelled out in a booklet, titled Navigating Tradition And Science – Singapore’s Approach In Determining The Hijri Calendar, published by Muis earlier in 2023.

Muis service transformation deputy director Muhammad Faizal Othman said former mufti Syed Isa Semait would use a calculator to come up with four or five pages of computations to determine the dates.

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Shaikh Syed Isa had first proposed Singapore’s adoption of the hisab method, and had himself studied astronomical calculation under an expert in Malaysia.

Now, however, this can be done with computer software, said Mr Faizal.

Mr Faizal is a local falak (astronomy) expert who serves as Singapore’s resource person in the Falak Committee of the Unofficial Meetings of Religious Ministers in Brunei, Indonesia, Malaysia and Singapore, or Mabims.

He previously served as a scientific officer at the Science Centre Singapore, where he was in charge of the observatory.

The accuracy of the dates can be proven by the accuracy in forecasting occurrences of eclipses, which can often be predicted down to the second, Mr Faizal told The Straits Times.

Only a handful of people here are currently knowledgeable in the field, he said, adding that he expects more to be trained in the science to aid Singapore’s efforts.

Q: Why do different countries celebrate Hari Raya on different dates?

A: Countries typically depend on observations of the new moon, or calculations predicting these observations, from their own locales.

Muis has said it is “not obligatory” for countries to follow one another in determining the date for the end of Ramadan, with Deputy Mufti Mohd Murat Md Aris stating that countries should rely on their own methods to determine the Islamic calendar.

While Mabims has criteria that act as a guide for each member country, these countries still have the autonomy to determine their dates for the new months.

“As such, should a new moon be sighted at one location in a certain country, signalling the beginning of the new month there, that does not necessarily apply to other countries,” the Mufti’s office said in a booklet.

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