Shared Night (Ikhtilaf al-Matali') in the Islamic Calendar
اشتراك الليل واختلاف المطالع في التقويم الإسلامي — شرح مفصل
The Fundamental Question
One of the most debated questions in Islamic jurisprudence regarding the lunar calendar is this: If the crescent moon is sighted in one location, does the new month begin for the entire world, or only for the location where it was sighted?
This question, known in Arabic as the issue of ikhtilaf al-matali' (اختلاف المطالع, "difference of horizons"), has been debated by Islamic scholars for over a millennium. The answer has profound practical implications — it determines whether Muslim communities around the world begin Ramadan on the same day or on different days.
The Three Major Scholarly Positions
Favored by: Hanafi school (majority view)
A crescent sighted anywhere in the world is valid for all Muslims everywhere. This position argues that the hadith "Fast when you see it" addresses the entire Muslim community collectively, not individual localities. Proponents point out that the Prophet did not specify "Fast when YOU see it in YOUR land," but used the collective pronoun.
Favored by: Shafi'i school (majority view)
Each region must rely on its own local crescent sighting. Different geographic regions may start Ramadan on different days. This position argues that the Earth is spherical and different locations have different horizons (matali’), so the crescent visible in Morocco is irrelevant to Muslims in Indonesia because it has not been sighted from their horizon.
Favored by: Compromise view (many contemporary scholars)
A crescent sighting is valid for all locations that "share the night" with the sighting location. If it is nighttime in both Casablanca and Mecca when the crescent is sighted in Casablanca, then Mecca can adopt that sighting. But if it is daytime in Jakarta when the sighting occurs, Jakarta cannot adopt it because they do not share the same night.
How Shared Night Works in Practice
The "shared night" principle works by checking whether two locations experience nighttime simultaneously. Consider this example:
Example Scenario:
📍 Casablanca, Morocco — Sunset at 19:30 UTC. The crescent is sighted at 19:50 UTC.
📍 Mecca, Saudi Arabia — Sunset at 16:00 UTC (already nighttime at 19:50 UTC). ✓ Shares the night → can adopt the sighting.
📍 Jakarta, Indonesia — Sunset at 10:30 UTC. At 19:50 UTC, it is 02:50 local time (already the next day's early morning). ⚠ Shares part of the night → scholars differ.
📍 Auckland, New Zealand — Sunset at 05:30 UTC. At 19:50 UTC, it is 07:50 the next morning. ✗ Daytime — does not share the night.
How Moon Visibility Explorer Implements Shared Night
Moon Visibility Explorer implements the shared night concept computationally. When generating a lunar calendar for a specific city, the tool performs the following analysis for each month:
- First, it checks whether the crescent is directly visible (Easily Visible or Visible under Perfect Conditions) at the selected city's coordinates.
- If the crescent is NOT directly visible, it scans the global 2°×2° visibility grid to find cells where the crescent IS visible.
- For each cell where the crescent is visible, it calculates the overlap of nighttime hours between that cell and the selected city.
- If sufficient nighttime overlap is found, the month start is marked as "Shared Night" and the source region is identified.
When viewing Night 1 on the map, cells that contributed to the shared night inheritance are highlighted in orange, making it visually clear why the month started on that date even though the crescent was not locally visible.
Which Countries Follow Which Approach?
| Approach | Countries |
|---|---|
| Global Sighting | Libya, some communities in Western countries |
| Local Sighting | Indonesia, Malaysia, Brunei, most of Southeast Asia |
| Shared Night / Regional | Saudi Arabia (often de facto), most Arab countries, Pakistan, many Sub-Saharan African countries |
| Calculated (no sighting) | Turkey, some European Islamic organizations, ISNA (North America) |
Explore Shared Night Analysis
To see shared night in action, generate a lunar calendar for any city and look for months marked with the shared night indicator. For more on the science behind visibility prediction, visit our Methodology page.