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Note: Lunar Data is updated at midnight at the Makkah Prime Meridian.

What is the Universal Hijri Calendar

The Universal Hijri Calendar (UHC), formulated by Sajid Mahmood Ansari, is a global, astronomy-based Hijri calendar system that unifies the Islamic lunar date for the entire Ummah while remaining faithful to the Shariah principle of moonsighting (ru’yat al-hilāl).

The Universal Hijri Calendar (UHC) is built on the fundamental Islamic and astronomical principle that a day is defined as a complete 24-hour cycle, not as a local or fragmented occurrence. Its core objective is to ensure that all Muslim countries enter a new Hijri month within the same 24-hour day, even if the exact moment of moon visibility differs slightly by region.

By using a unified astronomical framework grounded in the Moon’s actual motion and the Earth’s rotation, the UHC eliminates the long-standing problem of month fragmentation, where some countries begin a Hijri month one or even two days apart. Instead of forcing every region to start on the exact same clock hour, the UHC respects natural time zones while maintaining global unity at the day level, which is both scientifically sound and religiously meaningful.

This approach preserves the spirit of unity (Ummah) without violating the reality of Earth’s geography. Ramadan, Eid al-Fitr, Eid al-Adha, and all Hijri months begin within one continuous global day, allowing Muslims worldwide to observe key events in close harmony. In doing so, the Universal Hijri Calendar provides a practical, accurate, and unifying solution that aligns Islamic worship, astronomy, and the true definition of a day.

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Core Definition

The Universal Hijri Calendar is a luni-solar observational calendar framework in which:
A new Hijri month is deemed to have begun if the Moon reaches a geocentric elongation of 10 degrees or more from the Sun before the time of Fajr at the Makkah Prime Meridian, ensuring that the crescent has physically formed and entered the phase of potential visibility during that Islamic day.

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Foundational Principles

1. Makkah Meridian as the Prime Reference

The UHC adopts the Makkah Prime Meridian (≈ 39.8°E) as the zero-reference meridian for Hijri date transitions, replacing the politically defined Greenwich meridian.

We replace Greenwich with Makkah as the Prime Meridian in a purely civil, astronomical sense:

• Longitude 0° = Makkah
• Civil day = midnight-to-midnight
• The anti-meridian (±180°) lies at ≈ 140° W
• Therefore, a civil Hijri Date Line would indeed fall around 140° W

This choice is based on:

• Makkah is the Center of the Terrestrial surface
• The central religious significance of Makkah in Islam
• The Qur’anic role of the Ka‘bah as a focal point for worship and unity, particularly during the Hajj
• The need for a spiritually neutral and Ummah-centered longitudinal reference
• It also aligns with Medinah, the City of the Prophet Muhammad (peace be upon him)

All Hijri date changes are evaluated relative to Makkah time, not local or national horizons.

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2. Astronomical Conjunction (New Moon) as a Necessary Condition

• A Hijri month cannot begin before the astronomical conjunction (ijtima‘) of the Moon and Sun.
• Conjunction establishes the birth of the lunar month, but does not by itself start the month.

This preserves the classical Islamic understanding that visibility, not mere birth, defines the month.

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3. Possibility of Moonsighting (Imkān al-Ru’yah) as the Decisive Criterion

The UHC defines month commencement by the earliest date on which crescent sighting is astronomically possible, based on scientifically validated parameters, including:

• Luni-solar elongation
• Moon altitude at sunset
• Moon age after conjunction
• Lag time between sunset and moonset
• Atmospheric and optical constraints

A month begins on the Gregorian day whose sunset in the global region west of Makkah first satisfies credible visibility conditions.

This ensures:

• No month begins before the crescent could realistically be seen
• No dependence on politically restricted or erroneous local claims

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4. Global Unity of the Hijri Date

Once crescent visibility becomes possible anywhere on Earth, the Hijri date is uniformly applied to the entire world from the following sunset in Makkah time.

Thus:

• There is one Hijri date for the whole Ummah
• No regional fragmentation of months
• No retroactive corrections

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5. Shariah Compliance and Scientific Integrity

The UHC:

• Fully respects the Prophetic command of sighting the moon
• Avoids speculative or purely mathematical calendars
• Uses astronomy as a tool to evaluate possibility, not to replace ru’yah

It harmonizes:

• Classical fiqh principles
• Modern astronomical science
• Global administrative practicality

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Distinguishing Features

• Rejects purely local sighting chaos
• Rejects purely tabular calendars
• Prevents impossible 28-day lunar months
• Produces consistent 29/30-day months
• Allows long-term precomputation without violating Shariah

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