The Universal Hijri Calendar

Introduction

The Islamic calendar, also known as the Hijri calendar, is a purely lunar calendar used by Muslims around the world for religious observances and determining Islamic dates. It consists of 12 lunar months, each beginning with the sighting of the new moon, making it fundamentally tied to the phases of the moon. The length of each month is either 29 or 30 days, depending on the moon’s visibility, resulting in a total year length of approximately 354.3671 days—significantly shorter than the 365.2422-day tropical year used in the Gregorian calendar. In this article, we’ll focus on the Universal Hijri Calendar.

This shorter year means that the Islamic calendar does not align with the solar calendar and shifts approximately 10–12 days earlier each year in relation to the Gregorian calendar. As a result, Islamic months and significant dates, such as Ramadan, Eid al-Fitr, and Eid al-Adha, move through the seasons over time, completing a full cycle roughly every 33 solar years.

The Islamic calendar is rooted in divine guidance and religious tradition, as established in the Qur’an (Surah At-Tawbah, 9:36–37), where Allah declares the sanctity of 12 months ordained by Him. The verse emphasizes that four of these months—Dhul-Qa’dah, Dhul-Hijjah, Muharram, and Rajab—are sacred months in which war is prohibited, highlighting the importance of maintaining peace and reverence during these times.

Observing the Islamic calendar is not merely a matter of timekeeping but a sacred duty for Muslims, as it governs key religious practices, including the annual pilgrimage (Hajj), fasting in Ramadan, Zakat calculations, and the determination of Islamic holidays. It also serves as a reminder of Islamic history, particularly the Hijrah (migration) of the Prophet Muhammad (peace be upon him) from Makkah to Madinah in 622 CE, which marks the beginning of the Islamic era.

In addition to its religious significance, the lunar calendar reflects the natural rhythms of creation, symbolizing the cyclic nature of time and encouraging believers to reflect on the passage of life and the importance of accountability. This deep connection to nature and faith distinguishes the Islamic calendar as a spiritual framework that shapes the daily lives and rituals of Muslims worldwide.

Astronomical Significance of Makkah Prime Meridian

Most educated Muslims are aware that the Islamic Hijri calendar is a purely lunar calendar based on the lunation periods of the moon. It determines the Islamic months through lunar cycles, starting each month with the sighting of the new crescent moon (hilal). However, what is less commonly known is the astronomical and geographical foundation of the Hijri calendar and its connection to the Makkah Prime Meridian—a detail that highlights the scientific precision embedded within Islamic traditions.

The Islamic Hijri calendar was officially adopted by the Muslim community during the reign of Umar ibn Khattab (May Allah be pleased with him), the second Caliph of Islam. Its origin is intricately tied to the Hijrah (migration) of the Prophet Muhammad (peace and blessings be upon him and his family) from Makkah to Madinah, which marks the foundation of the first Muslim state. This migration symbolized the establishment of the first Muslim polity and served as a spiritual and historical turning point for the Muslim community, making it the logical choice as the starting point for the Islamic calendar.

Historical Context

Imam ibn al-Jawzi al-Hanbali (May Allah have mercy on him), in his treatise Al-Muntazam (an abridged and refined version of Tarikh al-Tabari), preserved valuable details regarding the adoption of the calendar.

He reports that:

Imam Saeed ibn al-Musayyib (May Allah have mercy on him) narrated:

“Umar (May Allah be pleased with him) gathered the people and asked them, ‘On which day should we begin the calendar?’ Ali ibn Abi Talib (May Allah be pleased with him) said, ‘From the day the Messenger of Allah, peace and blessings be upon him and his family, migrated and left the land of polytheism.’ Umar (May Allah be pleased with him) acted upon this.”

Uthman ibn Affan (May Allah be pleased with him) further advised:

“Date the first of Muharram as the beginning of the year.”

The author of the book (Imam Ibn al-Jawzi) clarified:

“They started dating ahead of two months or more because the Messenger of Allah, may Allah’s peace and blessings be upon him and his family, arrived in Medina on the 12th of Rabi’ al-Awwal.”

This decision established the Hijrah calendar as both a religious milestone and a practical system of timekeeping, reflecting the unity of the Muslim community.

The Makkah Prime Meridian and Astronomical Significance

A fascinating and lesser-known fact is that the Islamic Hijri calendar is based on the Makkah Prime Meridian. The 1st of Muharram, 1 Hijri, corresponds to the 15th of July 622 CE. This date holds astronomical significance—on this day, the sun reaches 90 degrees of altitude directly over the Meridian of Makkah, meaning the sun’s rays fall perpendicular to Makkah.

This alignment marks a solar zenith event over Makkah, making it a natural astronomical reference point for both timekeeping and calendar systems.

Why is 90 Degrees Altitude Significant?

1. Solar Alignment for Timekeeping:
   • The 90-degree altitude (solar zenith) is a definitive astronomical marker that occurs when the sun is directly overhead a specific location.
   • For ancient astronomers and calendar-makers, such zenith events were used to establish meridians and track solar cycles, serving as universal markers for measuring time.
2. Determining Noon (Solar Midday):
   • At the moment of solar zenith, shadows disappear, indicating true solar noon. Early Muslims needed to determine prayer times (salah), especially Dhuhr and Asr, as Islamic rituals rely heavily on solar movements for timekeeping.
3. Geographical and Religious Centrality of Makkah:
   • Makkah’s astronomical alignment highlights its status as the spiritual and geographical center of Islam.
   • It symbolizes the unity of Muslims worldwide who face Makkah (Qibla) during prayers, further integrating faith and science into Islamic practices.
4. Seasonal and Agricultural Markers:
   • The sun’s position at 90 degrees also relates to seasonal cycles, which influenced traditional agricultural practices in the Arabian Peninsula. Although the Hijri calendar is lunar, this solar alignment adds a layer of practical observation for agricultural timing and crop harvesting cycles.

The Hijri calendar is more than a lunar system; it is a fusion of faith, astronomy, and history. It reflects the spiritual significance of the Hijrah, the centrality of Makkah, and the scientific awareness of early Muslims who aligned their calendar with celestial phenomena.

By anchoring the Islamic timeline to the Makkah Prime Meridian and connecting it with solar observations, the Hijri calendar underscores the harmonious relationship between faith and science in Islam, offering Muslims a framework for both spiritual devotion and scientific exploration.

Hijri Calendar and Makkah Prime Meridian

The association of the Hijri calendar with the Makkah Prime Meridian is not only a remarkable feature but also a profound testament to the centrality of Makkah in the Islamic worldview. This connection emphasizes that the Hijri calendar is inherently aligned with Makkah time, reflecting its spiritual, historical, and astronomical significance. Such alignment highlights the need for a unified approach to the Islamic calendar, ensuring consistency and harmony across the Muslim Ummah.

The Principle of Unity in Timekeeping

Since the Hijri calendar is based on lunar months and its starting point (1st Muharram, 1 AH) is linked to a precise astronomical event—the solar zenith over Makkah—it inherently supports the principle of a universal time standard. The lunar phases are observable phenomena, visible to people across the globe, making it scientifically feasible to establish a unified Hijri date worldwide.

This means that on any given specific day, there should logically be one single Hijri date observed by all Muslims, regardless of geographical location. The existence of multiple Hijri dates on the same Gregorian day, as is currently the case in many parts of the Muslim world, contradicts this scientific and theological principle and undermines the uniformity and unity that Islam seeks to promote.

Addressing the Issue of Divergent Hijri Calendars

At present, many Muslim countries and communities rely on local moon sightings to determine the beginning of each lunar month, leading to variations in the declaration of important dates, such as Ramadan, Eid al-Fitr, and Eid al-Adha. These differences often cause confusion, division, and disruption in observing these sacred occasions. For example:

• Some regions may start Ramadan a day earlier or later than others.
• Eid celebrations may fall on different days, even within the same country or neighboring areas.

This fragmentation contradicts the spirit of unity that Islam emphasizes, particularly during collective acts of worship like fasting and prayers. It also creates practical challenges for Muslim communities living in non-Muslim countries, where public holidays and workplace accommodations depend on fixed dates.

The Case for a Universal Hijri Calendar

The scientific connection between the Hijri calendar and the Makkah Prime Meridian provides a compelling foundation for establishing a universal Islamic calendar. By standardizing the calendar based on Makkah time and lunar calculations, Muslims can:

1. Unite the Global Ummah:
   • A universal Hijri calendar would foster global unity and synchronization of religious observances.
   • It would reinforce the centrality of Makkah as the spiritual axis for all Muslims, symbolizing solidarity and cohesion.
2. Ensure Accuracy and Reliability:
   • Modern astronomical calculations can accurately predict moon phases, removing uncertainties related to local sightings and ensuring reliable date-setting.
   • Such precision would align Islamic practices with scientific advancements, reflecting Islam’s emphasis on knowledge and rationality.
3. Simplify Religious Observances:
   • Muslims living in different time zones and minority communities would no longer face confusion or isolation in celebrating festivals.
   • A fixed calendar would make it easier for schools, businesses, and governments to accommodate Islamic holidays, promoting greater inclusivity.
4. Revive Islamic Heritage in Astronomy:
   • The move toward a global Hijri calendar would reclaim Islam’s legacy of scientific achievements, particularly in astronomy and timekeeping.
   • It would highlight the Qur’an’s call to observe the natural signs in the heavens as markers for time and guidance (Qur’an 10:5).

Overcoming Challenges to Implementation

While the concept of a universal Hijri calendar is grounded in both scripture and science, achieving global adoption requires addressing several challenges:

1. Religious Traditions and Interpretations:
   • Some scholars and regions strongly adhere to the physical sighting of the moon as the basis for marking Islamic months.
   • A universal calendar would need consensus among Islamic scholars (Ulama) to harmonize traditional methods with scientific calculations.
2. Political and National Divisions:
   • Different countries may resist abandoning their independent lunar calendars due to political rivalries or national sovereignty concerns.
   • Efforts must focus on dialogue and collaboration through international bodies like the Organization of Islamic Cooperation (OIC).
3. Public Awareness and Education:
   • Educating Muslims about the scientific and spiritual validity of a calculated Hijri calendar is crucial to gaining public support.
   • Campaigns highlighting the Makkah Prime Meridian and its role in unifying timekeeping can help address misconceptions.

The Hijri calendar’s connection to the Makkah Prime Meridian is a powerful symbol of the unity and precision embedded within Islamic teachings. Establishing a universal Islamic calendar, synchronized with Makkah time and based on scientific lunar calculations, is not just a practical necessity but also a spiritual imperative. It would:

• Unify Muslims globally in religious observances.
• Enhance the accuracy and predictability of Islamic dates.
• Showcase Islam’s harmony with science and its emphasis on knowledge.

In an age of global interconnectedness, such a calendar would eliminate fragmentation, strengthen the Muslim Ummah, and honor the legacy of Islamic astronomy, fulfilling both religious obligations and modern needs.

Universal Hijri Claendar & Makkah Prime Meridian

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The Makkah Prime Meridian holds a central and sacred position in the Islamic worldview, making it the most appropriate reference point for determining the beginning of the Islamic months. This approach not only aligns with the spiritual significance of Makkah al-Mukarramah but also provides a unified framework for the Muslim Ummah to establish a consistent and reliable Islamic calendar.

The Importance of Makkah in Timekeeping

The most celebrated event for Muslims worldwide is the Hajj pilgrimage, which is entirely centered on Makkah. The Islamic calendar, therefore, should reflect this geographical and spiritual centrality to preserve uniformity in religious observances. For example:

• The Day of Arafah (9th Dhul-Hijjah) and Eid al-Adha (10th Dhul-Hijjah) are directly tied to the rituals of Hajj in Makkah.
• Ensuring that all Muslims observe these events synchronously reinforces the unity of the Ummah and avoids fragmentation caused by regional variations in moon sightings.

Additionally, the 1st of Muharram—marking the beginning of the Hijri year—is astronomically significant because it should always correspond to the same day of the week (Thursday) after 33 lunar years, completing a larger lunar cycle. This periodic alignment demonstrates the mathematical and astronomical precision of the Hijri calendar and further supports the case for standardizing its observance based on the Makkah Prime Meridian.

Key Considerations for Associating Islamic Months with Makkah Time

To create a scientifically sound and religiously consistent calendar, the following points must be considered when associating the beginning of Islamic months with the Makkah Prime Meridian:

1. New Moon (Hilal) is Sighted After Sunset:
   • The Islamic month begins with the sighting of the crescent moon (hilal) following sunset.
   • This method is deeply rooted in Islamic tradition, where the Prophet Muhammad (peace be upon him) instructed Muslims to begin fasting and celebrate Eid based on moon sightings.
   • By tying the observation of the hilal to Makkah’s horizon, the time zone variations and local discrepancies can be eliminated.
2. Daytime Moon Sightings May Be Considered, But the Month Begins After Sunset:
   • If the moon is sighted during the daytime, it can be considered for astronomical calculations.
   • However, the official start of the new month must follow the sunset in Makkah, maintaining adherence to Islamic jurisprudence and preserving the connection to lunar cycles.
   • This approach ensures that tradition and science complement each other, fostering accuracy without disregarding Islamic principles.
3. Moon Sighted West of Makkah Must Be Before Fajr:
   • If the crescent moon is observed west of Makkah, it can still be considered, provided it occurs before Fajr (dawn) at Makkah’s horizon.
   • This allows for slight variations in timing while maintaining the primacy of Makkah’s location as the reference point.
   • Such flexibility accommodates regional visibility without breaking the principle of unity under a Makkah-centered calendar.

Establishing a Unified Calendar Based on Astronomical Calculations

Given the advancements in astronomy, it is now possible to calculate the visibility of the crescent moon with a high degree of accuracy. Combining observational methods with astronomical predictions provides an opportunity to create a universal Hijri calendar that adheres to Islamic principles while leveraging modern science.

The proposed calendar would:

1. Use Makkah Time as the Standard:
   • All calculations and date determinations would be based on the Makkah Prime Meridian.
   • The solar and lunar cycles relative to Makkah’s horizon would establish a unified framework for the Islamic calendar.
2. Account for Possible Moon Sightings Before Fajr at Makkah:
   • The month would only begin if the crescent moon could reasonably be sighted before Fajr in Makkah’s horizon, ensuring consistency with traditional methods of observation.
3. Integrate Scientific Data with Religious Observances:
   • Incorporate astronomical calculations for moon visibility while respecting Islamic injunctions about local sightings and sunset-based beginnings.
   • Provide a framework for synchronized observances of Ramadan, Eid, and Hajj, uniting Muslims worldwide.
4. Maintain the 33-Year Lunar Cycle Alignment:
   • Ensure that the 1st of Muharram aligns with the same day of the week every 33 years, reflecting the lunar cycle’s periodic precision and reinforcing the accuracy of the proposed calendar.

Computed Universal Hijri Calendar

By incorporating Islamic traditions and scientific observations we can devise a computed Universal Hijri calendar for not only civil purposes but for religious observances as well.

The start of a new Islamic month is determined by the following conditions:

1. Lunisolar Elongation and Moon Altitude:
   • The combined elongation and altitude of the moon, in any location across the world, must reach 15 degrees before Fajr at Makkah.
   • Elongation refers to the angular distance between the Sun and the Moon, and altitude refers to the moon’s angle above the horizon.
2. Global Applicability:
   • This criterion is applicable universally, meaning that the time of Fajr at Makkah is used as a reference for all Muslim communities around the world.
   • If the 12-degree criterion is met before Fajr at Makkah, it marks the first night of the new month, and the following day is considered the first day of the Islamic month.
3. Buffer Zone:
   • If the combined elongation + altitude is in the range of 11-12 degrees, the start of the new month may still be recognized if the moon’s visibility is predicted or expected later that night.
4. Local Sightings and Observations:
   • While astronomical calculations form the primary basis for determining the start of the month, local sightings may be considered in cases where astronomical predictions and actual visibility may differ (e.g., due to weather conditions).

Why not New Moon or Optical Aid?

Our reasoning for not incorporating telescopic visibility of the moon into the Universal Hijri Calendar is both logical and well thought out. The primary concern is that, even with the aid of optical instruments, the crescent moon can sometimes be visible before Fajr at Makkah, even if the New Moon’s birth occurs after sunset at Makkah. Even with the aid of optical instruments, the crescent moon can sometimes be visible after Fajr at Makkah, while the New Moon’s birth occurs after Fajr at Makkah. It does not make sense.

By excluding telescopic visibility after Fajr and focusing on astronomical criteria (such as the 15-degree threshold for elongation and altitude), we are ensuring that the Universal Hijri Calendar remains consistent, predictable, and aligned with the timing of the New Moon birth and the global start of the new Islamic month. This method provides clarity and unity across the Muslim Ummah and reduces the risks of discrepancies caused by localized telescopic sightings, especially those occurring after Fajr at Makkah.

The New Moon, often referred to as the dark moon, occurs when the Moon is positioned between the Earth and the Sun in such a way that its illuminated side faces away from the Earth. This alignment results in a lunisolar elongation (angular separation) of zero degrees, meaning the Moon and the Sun share the same celestial longitude. Consequently, the Moon appears completely dark to observers on Earth and is invisible to the naked eye.

Why Does the New Moon Remain Invisible?

1. Sun’s Glare:
   • During the New Moon phase, the Moon is so close to the Sun in the sky that its faint crescent, if present, is overwhelmed by the Sun’s bright light.
   • This proximity to the Sun makes it impossible to distinguish the Moon from the background sky during the daytime.
2. Lack of Illumination:
   • At zero elongation, the near side of the Moon (the side facing Earth) is not illuminated by sunlight, rendering it completely dark and invisible.
   • As the elongation angle gradually increases, sunlight begins to illuminate a small portion of the Moon’s surface, creating a crescent shape that eventually becomes visible.
3. Invisible Transition Period:
   • Even after the New Moon phase, when the angular separation between the Moon and the Sun begins to increase, the crescent moon remains invisible for several hours (sometimes more than 20 hours) due to its proximity to the Sun and the need for the crescent to develop sufficient illumination and altitude to rise above the horizon at twilight.
4. Dependence on Elongation and Altitude:
   • Observing the crescent moon requires a minimum elongation angle (angular distance from the Sun) and a certain altitude above the horizon.
   • For naked-eye observation, this elongation is typically around 7.5 degrees (Danjon Limit), but for optical instruments, it can be as small as 1-2 degrees.
   • However, even at these low elongation values, visibility is influenced by atmospheric conditions, geography, and timing (sunset or sunrise).
5. Geometric Alignment and Time Delay:
   • The New Moon birth (conjunction) does not immediately lead to crescent visibility because the Moon must move far enough away from the Sun to reflect sufficient light toward Earth.
   • This delay between the New Moon phase and the first visibility of the crescent depends on the observer’s location, atmospheric clarity, and the time of sunset or sunrise.

Scientific and Islamic Implications:

• The New Moon is used as a reference point for astronomical calculations, but the Islamic calendar relies on the actual sighting of the crescent moon (Hilal) to mark the beginning of a new month.
• Since the crescent visibility depends on the angular separation (elongation) and altitude, the phase immediately following the New Moon (when the elongation increases) becomes critical for calendar synchronization.
• For the Universal Hijri Calendar, this emphasizes the need to establish a scientific threshold—such as the 15-degree combined elongation and altitude criterion—to predict crescent visibility globally and standardize the start of Islamic months.

It is notable that at the time of lunisolar conjunction—commonly referred to as the New Moon—another significant natural phenomenon often occurs, namely a solar eclipse. This astronomical alignment highlights the dark moon phase, during which the Moon is positioned directly between the Earth and the Sun, casting a shadow on the Earth and temporarily blocking the Sun’s light in specific regions.

Historical Context in the Life of Prophet Muhammad (peace be upon him):

In the life of Prophet Muhammad (peace be upon him), after the Hijrah (migration to Madinah), solar eclipses were recorded to have occurred twice:

1. First Solar Eclipse:
   • Date: 29th Shawwal, 10 AH (January 27, 632 CE)
   • This event coincided with the death of the Prophet’s son, Ibrahim.
   • People initially speculated that the eclipse was linked to Ibrahim’s death, but the Prophet (peace be upon him) clarified that solar eclipses are natural signs of Allah’s power and are not related to human events.
2. Second Solar Eclipse:
   • Another solar eclipse occurred during his lifetime, but there is no record indicating that it was used to mark the beginning of an Islamic month or to adjust the Hijri calendar.

Key Lessons Derived from These Events:

1. The Dark Moon Marks the End, Not the Beginning, of the Month:
   • The occurrence of a solar eclipse during the New Moon phase demonstrates that the dark moon is not visible and cannot be used as the beginning of an Islamic month.
   • Instead, the dark moon represents the last phase of the lunar cycle, indicating the end of the current Islamic month rather than the start of a new one.
2. Emphasis on Visibility of the Crescent Moon (Hilal):
   • The Prophet (peace be upon him) never began an Islamic month based on the astronomical New Moon or its associated solar eclipse.
   • Instead, he instructed his followers to look for the crescent moon (Hilal) after sunset to determine the beginning of a new month, especially for significant months like Ramadan. Shawwal and Dhul Hijjah.
   • It is narrated from Abu Huraira (may Allah be pleased with him) that the Prophet (peace be upon him) said:
   • “Fast upon seeing the crescent (Hilal) and end the fast upon seeing the crescent (Hilal).”
   • References: Musnad Ahmad: Hadith 9365, Sahih Bukhari: Hadith 1909, Sahih Muslim: Hadith 1081
   • In another other narration the words are as follows:
   • إِذَا رَأَيْتُمُ الْهِلَالَ فَصُومُوا، وَإِذَا رَأَيْتُمُوهُ فَأَفْطِرُوا، فَإِنْ غُمَّ عَلَيْكُمْ فَصُومُوا ثَلَاثِينَ يَوْمًا
   • The Prophet (peace be upon him) said:
   • “When you see the crescent moon (Hilal), then begin fasting, and when you see it (again), then end your fasting. But if it is obscured (cloudy), then complete thirty days (of fasting).”
   • Reference: Sahih Muslim (1081)
   • This highlights that Islamic months should start with the visibility of the crescent moon rather than relying solely on astronomical calculations of the New Moon phase.
3. Distinction Between Astronomical Events and Religious Observances:
   • While solar eclipses and lunisolar conjunctions are important astronomical events, they are not indicators for marking religious observances.
   • The Prophet (peace be upon him) established prayers (Salat al-Kusoof) during solar eclipses as a means to remember Allah, rather than using the event as a calendar marker for starting an Islamic month.
4. Dark Moon as a Transition Phase:
   • The dark moon (New Moon) serves as a transition from one lunar cycle to another but does not hold visibility or symbolic significance in the Islamic lunar calendar.
   • Its invisibility underscores that the new Islamic month begins only after the crescent moon (Hilal) becomes visible, which typically occurs one or two days after the New Moon’s birth.
5. Scientific Validation of Religious Practices:
   • Modern astronomical calculations confirm the alignment of the New Moon phase with solar eclipses, yet Islamic tradition aligns more closely with the visual sighting of the crescent moon, reaffirming the Prophet’s (peace be upon him) method of determining time through observation rather than abstract astronomical models.

Implications for the Universal Hijri Calendar:

• The Prophet’s practice of not starting months based on the dark moon reinforces the idea that the Islamic calendar must rely on crescent visibility rather than the astronomical New Moon birth.
• This historical evidence supports the 15-degree elongation and altitude criterion, which ensure that the crescent moon can potentially be sighted before Fajr at Makkah, even if visibility is enhanced through calculated predictions rather than purely local sightings.

The occurrence of solar eclipses during the dark moon phase in the Prophet’s lifetime provides clear evidence that the Islamic calendar does not start with the astronomical New Moon (dark moon). Instead, the crescent moon (Hilal) marks the beginning of a new month, emphasizing visual observation over conjunction calculations. This principle forms the foundation for establishing a Universal Hijri Calendar, ensuring it remains faithful to both Islamic traditions and scientific advancements in astronomical calculations.

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