The religious basis: Sighting the hilal
Ramadan begins with the sighting of the new crescent moon (hilal) following the astronomical new moon. The Islamic calendar is strictly lunar, with months lasting either 29 or 30 days.
The Prophet Muhammad said, “Fast when you see it and break your fast when you see it.” For centuries, this instruction has been interpreted as requiring visual confirmation of the crescent to mark the start of a new month.
In Egypt, the official announcement is issued by Dar Al-Ifta in coordination with the National Research Institute of Astronomy and Geophysics.
Observation committees are dispatched across the country on the evening of the 29th of Shaaban to attempt sighting at sunset.
If the crescent is confirmed, Ramadan begins the following day. If not, Shaaban completes 30 days.
The astronomical dimension: Why visibility is complicated
Astronomically, the new moon occurs when the moon and sun share the same celestial longitude, a moment called conjunction. However, at conjunction, the moon is invisible because it lies too close to the sun’s glare.
For the crescent to be visible, the moon must be sufficiently separated from the sun, at an elongation angle; it must set after sunset; it must have adequate altitude above the horizon; and atmospheric conditions must permit visibility.
Even if the conjunction occurs before sunset, the crescent may be too thin or too low to be seen.
Institutions such as the International Astronomical Centre publish detailed visibility maps each month that show where sight is possible, impossible, or requires optical aid.
Thus, two countries observing on the same evening may reach different conclusions based on physics alone.
Geography: The Earth is not uniform
Because the Earth rotates and sunset occurs at different times across longitudes, crescent visibility varies by location.
For example, a crescent may be impossible to see in Indonesia at sunset. However, the same crescent could be visible hours later in North Africa or South America.
This spatial variation explains why Western Hemisphere countries sometimes confirm sightings when Eastern Hemisphere countries do not.
Jurisprudential differences: Local vs global sighting
Islamic legal schools differ on whether moon sighting must be local or can be accepted globally.
1. Local sighting
Some scholars maintain that each region must rely on its own confirmed sighting due to geographical differences. Countries following this approach will not automatically adopt another country’s announcement.
2. Global sighting
Other scholars argue that a verified sighting anywhere in the Muslim world suffices for all.
3. Calculation-based approach
A growing number of authorities accept astronomical calculations as decisive, especially when visibility is scientifically impossible. Countries like Turkey rely almost entirely on pre-calculated lunar calendars.
Meanwhile, Saudi Arabia bases its announcement on Supreme Court rulings, supported by testimony from local observers.
Because no central Islamic authority governs all Muslims worldwide, national religious bodies retain autonomy in decision-making.
The role of science in modern decisions
Today, most religious authorities consult astronomers before issuing a decision. Scientific data can determine whether sighting is theoretically possible or impossible.
In Egypt, scientific reports are submitted to Dar Al-Ifta before the Mufti issues the final ruling. While jurisprudence ultimately governs the decision, scientific input plays a critical advisory role.
Many scholars argue that announcing sighting when astronomy proves visibility impossible undermines credibility. Others emphasize adherence to traditional testimony procedures.
The debate reflects broader discussions about the relationship between revelation and scientific certainty.
Weather and seasonal effects
Weather remains a decisive factor. Cloud cover, dust storms, humidity, and light pollution can obstruct visibility even when astronomical conditions are favourable.
Ramadan shifts backwards by 10–11 days each solar year. For several consecutive years, it falls during winter in the Northern Hemisphere, a season often marked by heavier cloud cover in parts of the Middle East and North Africa.
Thus, even within a single country, conditions can vary regionally.
Why hasn’t a unified Islamic calendar been adopted?
Over the past decades, conferences of scholars and astronomers have proposed a unified global lunar calendar based on precise astronomical calculations.
Supporters argue that astronomy now provides exact data, would eliminate confusion and annual disputes, and would simplify scheduling for global Muslim communities.
Opponents counter that the prophetic tradition emphasizes visual sighting, jurisprudential diversity is legitimate, and local authority remains important.
To date, no global consensus has been reached.
Does the difference undermine unity?
Religious scholars widely consider these differences legitimate within Islamic jurisprudence. A one-day variation does not invalidate fasting or religious observance.
Historically, differences in moon sighting occurred even in early Islamic communities due to geographical separation.
For many scholars, diversity in interpretation reflects flexibility rather than division.
The bottom line
Ramadan’s start date may differ from country to country because of the following:
- Crescent visibility varies geographically.
- Jurisprudential schools differ in interpretation.
- Some rely on local sightings; others accept global reports.
- Some prioritize calculation; others require visual confirmation.
- Weather conditions affect observation.
The variation is therefore not an error, but the result of combining religious tradition, astronomical science, and national authority within a global faith community.
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