official saudi arabia calendar! تقويم أم القرى! Umm Al Qura Calendar!
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Umm al-Qura Calendar: How Saudi Arabia’s Official Hijri Calendar Works
The Umm al-Qura calendar is the official Hijri civil calendar used by the government of Saudi Arabia. It is designed to determine the start of Hijri months in advance through fixed astronomical calculations rather than real-time visual moon sighting. This approach allows dates to be known ahead of time for administrative, legal, and planning purposes.
Unlike traditional observational calendars that depend on physical sighting of the lunar crescent, the Umm al-Qura calendar applies a predefined calculation method based on astronomical data for Mecca.
The Two-Condition Rule System
In the Umm al-Qura calendar, the decision about the length of a month is made on the 29th day of the current lunar month. Two specific astronomical conditions are evaluated using calculations centered on Mecca. These conditions determine whether the following day will begin a new Hijri month or whether the current month will be completed as a 30-day month.
Condition 1: Conjunction Before Sunset
The first condition examines the timing of the astronomical conjunction of the Moon and the Sun. Conjunction occurs when the Moon and the Sun share the same ecliptic longitude, marking the moment of the new moon in astronomical terms. For the first condition to be satisfied, this conjunction must occur before sunset in Mecca on the 29th day of the current month.
Condition 2: Moonset After Sunset
The second condition evaluates the setting times of the Moon and the Sun on the same day. Specifically, the Moon must set after the Sun in Mecca. If the Moon remains above the horizon after sunset, this condition is considered fulfilled. If the Moon sets before the Sun, the condition is not met, regardless of when conjunction occurred.
Decision Logic
When both conditions are satisfied—conjunction before sunset and moonset after sunset—the following day is designated as the first day of the new Hijri month. If either condition is not satisfied, the current month is extended to complete 30 days, and the new month begins on the day after that. This rule ensures that all months remain either 29 or 30 days long and remain aligned with the lunar cycle.
How the Decision Process Works
The table below illustrates how different combinations of the two conditions determine month length:
| Conjunction Before Sunset (Mecca) | Moonset After Sunset (Mecca) | Result | Current Month Length |
|---|---|---|---|
| ✅ Yes | ✅ Yes | New month begins next day | 29 days |
| ✅ Yes | ❌ No | Current month continues | 30 days |
| ❌ No | ✅ Yes | Current month continues | 30 days |
| ❌ No | ❌ No | Current month continues | 30 days |
Key principle: Both conditions must be met simultaneously on the 29th day for the month to end at 29 days. If either condition fails, the month completes 30 days.
Why Mecca is the Reference Point
All calculations in the Umm al-Qura calendar use Mecca (21.4225° N, 39.8262° E) as the geographic reference point. This choice serves multiple purposes:
- Religious significance: Mecca holds central importance in Islamic practice, making it a natural reference point for a Hijri calendar system used in Saudi Arabia.
- Consistency: Using a single fixed location eliminates variations that would occur if different cities or regions calculated independently.
- Administrative uniformity: Government institutions, businesses, schools, and public services across Saudi Arabia can operate on synchronized dates without regional discrepancies.
The sunset time in Mecca and the Moon’s position relative to Mecca’s horizon are the only geographic factors that matter in the calculation. The system does not consider visibility conditions, weather, atmospheric refraction, or actual observation capability.
Astronomical Data Requirements
To apply the Umm al-Qura rules, the following astronomical values must be calculated for the 29th day of each Hijri month:
- Conjunction time: The precise moment (to the minute) when the Moon and Sun reach the same ecliptic longitude, expressed in Mecca local time.
- Sunset time in Mecca: The moment when the Sun’s upper edge disappears below the horizon, adjusted for Mecca’s elevation and standard atmospheric refraction.
- Moonset time in Mecca: The moment when the Moon’s upper edge disappears below the horizon, calculated using the Moon’s actual position and Mecca’s local horizon.
These values are computed using established astronomical algorithms that account for the Moon’s orbital mechanics, the Sun’s apparent motion, Earth’s rotation, and geographic coordinates. The calculations can be performed years in advance with high precision.
Practical Applications
Because these rules rely entirely on calculated astronomical data, the Umm al-Qura calendar provides a predictable and uniform date system. The calendar is widely used for:
- Government operations: Official documents, legal contracts, court proceedings, and administrative deadlines reference Umm al-Qura dates.
- Education calendars: School terms, examination schedules, and academic year planning use predetermined Hijri dates.
- Payroll and financial cycles: Salary disbursement, billing periods, and fiscal reporting align with known calendar dates.
- Public holidays: National holidays and official observances are scheduled using the civil calendar.
- Long-term planning: Multi-year projects, construction timelines, and policy implementation schedules require advance date certainty.
Civil Calendar vs. Religious Observance
It is important to distinguish between the civil function of the Umm al-Qura calendar and religious observance practices. While the calendar provides an official civil date reference, religious observances in many Muslim communities continue to rely on actual moon sighting or locally accepted religious authorities.
Why Differences Occur
- Methodology variation: Traditional moon sighting depends on atmospheric conditions, observer location, and visual confirmation. Calculated calendars use mathematical models that may produce different results.
- Geographic scope: A crescent visible in one region may not be visible in another due to horizon differences, making regional variations common in observational systems.
- Religious authority: Different communities follow different scholarly opinions on acceptable sighting methods, witness requirements, and geographic scope for moon sighting validity.
- Calculation parameters: Even among calculated calendars, different systems use different criteria (elevation angle, time lag, geographic reference) leading to date variations.
The Umm al-Qura calendar does not claim to resolve these differences. It serves as a civil administrative tool, not a religious authority.
Month Length Distribution
The following table shows the twelve Hijri months and their typical length patterns in the Umm al-Qura calendar:
| Month Number | Month Name | Typical Length | Notes |
|---|---|---|---|
| 1 | Muharram | 29 or 30 days | Varies by calculation |
| 2 | Safar | 29 or 30 days | Varies by calculation |
| 3 | Rabi’ al-Awwal | 29 or 30 days | Varies by calculation |
| 4 | Rabi’ al-Thani | 29 or 30 days | Varies by calculation |
| 5 | Jumada al-Awwal | 29 or 30 days | Varies by calculation |
| 6 | Jumada al-Thani | 29 or 30 days | Varies by calculation |
| 7 | Rajab | 29 or 30 days | Varies by calculation |
| 8 | Sha’ban | 29 or 30 days | Varies by calculation |
| 9 | Ramadan | 29 or 30 days | Varies by calculation |
| 10 | Shawwal | 29 or 30 days | Varies by calculation |
| 11 | Dhu al-Qi’dah | 29 or 30 days | Varies by calculation |
| 12 | Dhu al-Hijjah | 29 or 30 days | Varies by calculation |
Each month’s actual length in any given year depends on whether the two-condition rule is satisfied on that month’s 29th day. There is no fixed alternating pattern.
Historical Context
The Umm al-Qura calendar system was developed to address practical needs in modern administration. Before its adoption, reliance on visual moon sighting made advance planning difficult for government operations, educational institutions, and business scheduling.
The system takes its name from Mecca, which is referred to as Umm al-Qura (أم القرى), meaning “Mother of Cities” in Arabic. By establishing astronomical calculation rules centered on Mecca, Saudi Arabia created a calendar that balances Islamic tradition with administrative practicality.
The calendar has undergone refinements since its introduction to improve astronomical accuracy and computational consistency. Modern implementations use precise ephemeris data and standardized calculation methods to ensure long-term reliability.
What This Page Does and Does Not Do
This page explains the calculation method used by the Umm al-Qura civil calendar for determining Hijri month starts. It does not determine religious rulings, announce the beginning of Islamic months for worship, or replace traditional moon sighting practices.
For religious observance dates, consult local religious authorities or moon sighting committees in your region.
Umm al-Qura Calendar Apps & Tools
Official tools and extensions for accessing Umm al-Qura Hijri calendar dates for reference and informational use.CTA: View Tools
What is the Umm al-Qura calendar?
The Umm al-Qura calendar is Saudi Arabia’s official civil Hijri calendar system. It uses predetermined astronomical calculations based on Mecca’s coordinates to determine when each Hijri month begins, allowing dates to be known years in advance for administrative purposes.
Is the Umm al-Qura calendar used for religious purposes?
No. The Umm al-Qura calendar is a civil administrative calendar used by the Saudi government for planning, scheduling, and official documentation. Religious observances, including the start of Ramadan and Eid celebrations, often continue to rely on actual moon sighting or local religious authorities. Differences between civil and religious dates can and do occur.
Why do some countries have different Hijri dates than Saudi Arabia?
Different countries use different methods to determine Hijri dates. Some rely on local moon sighting, others use global sighting criteria, and some use calculated calendars with different astronomical parameters. The Umm al-Qura calendar uses specific calculation rules centered on Mecca, which may produce different results than methods used elsewhere.
Can Umm al-Qura dates be calculated years in advance?
Yes. Because the calendar relies entirely on astronomical calculations rather than actual observation, dates can be computed with high accuracy years or even decades in advance. This predictability is essential for long-term government planning, academic calendars, and administrative scheduling.
What happens if both astronomical conditions are not met on the 29th day?
If either condition fails—conjunction occurs after sunset, or the Moon sets before the Sun—the current month automatically extends to 30 days. The new month then begins on the following day. This ensures all months are either 29 or 30 days long with no exceptions.
Why is Mecca used as the reference point for all calculations?
Mecca serves as the single geographic reference point for consistency across Saudi Arabia. Using one fixed location eliminates regional variations and ensures uniform dates for all government institutions, businesses, and public services throughout the country. The choice also reflects Mecca’s religious and cultural significance.