official saudi arabia calendar! تقويم أم القرى! today islamic date in saudi arabia!
today arabic date in KSA! saudi calendar!

Umm al-Qura Calendar

Umm al-Qura calendar is Saudi Arabia’s official Hijri (Islamic) civil calendar, created using precise astronomical calculations rather than last-minute naked-eye moon sightings. This calendar is the backbone of timekeeping in the Kingdom, used for government planning, court schedules, payroll cycles, academic timetables, travel bookings, and public holidays. Because it is deterministic and predictable, it can be relied upon for long-term planning without waiting for clear skies or moon-sighting announcements.

For anyone who wants to know today’s Islamic Date, plan months ahead, or develop software that needs accurate Islamic dates, the Umm al-Qura calendar is the gold standard. In this guide, we’ll explore its history, methodology, formulas, advantages, and practical use cases — in a way that is easy to understand for students, researchers, and developers alike.

What Is the Umm al-Qura Calendar?

Umm al Qura calendar is a lunar calendar based on the Islamic Hijri system, which tracks time according to the phases of the Moon. Like all Hijri calendars, it has twelve lunar months, each with 29 or 30 days, giving a year that is about 10–11 days shorter than the Gregorian solar year.

Where traditional calendars rely on human sighting of the crescent moon (hilāl), Umm al-Qura uses astronomical data and a simple two-step rule to decide whether the month ends on the 29th or extends to 30 days. This makes it a scientific yet faith-aligned solution for modern society.

Why Saudi Arabia Uses It for Civil Timekeeping

Running a country requires predictability and uniformity. Imagine if schools, courts, airlines, and businesses all used different Hijri dates because some saw the moon and others didn’t. The Umm al-Qura calendar solves this by providing one official reference, tied to Mecca, that the entire nation follows.

This means:

• School terms and examination dates can be announced months in advance.

• Public holidays like Eid can be listed early in government gazettes.

• Businesses can set payroll deadlines, tax due dates, and contracts without confusion.

• Pilgrims planning Hajj and Umrah can align flights, hotel bookings, and visas with confidence.

How Umm al Qura calendar Is Work?

At the core of the Umm al-Qura calendar is a two-condition test applied on the 29th evening of every lunar month in Mecca. These conditions use precise astronomical calculations to check whether it is permissible to start the next month the following day.

Step 1 – Conjunction Time (Astronomical New Moon)

The conjunction, also called the astronomical new moon, is the exact moment when the Sun, Moon, and Earth are aligned on the same celestial longitude. At this moment, the Moon is not visible from Earth, as it is directly between the Earth and the Sun.

• Formula Concept:
  Conjunction occurs when the ecliptic longitude of the Moon (λₘ) equals the ecliptic longitude of the Sun (λₛ):
  λₘ = λₛ

If this conjunction happens before sunset in Mecca, this condition is satisfied. If it occurs after sunset, the new month cannot begin the next day.

Step 2 – Moonset After Sunset

The second condition is purely geometric. The Moon must still be above the horizon at sunset so that it is theoretically possible for the crescent to be seen (even if not actually sighted due to clouds or brightness).

• Formula Concept:
  Calculate the local times of sunset and moonset for Mecca:

  • Sunset = when the Sun’s upper limb crosses the local horizon (altitude = 0°).

  • Moonset = when the Moon’s upper limb crosses the horizon (altitude = 0°).
    If Moonset Time > Sunset Time, this condition passes.

Final Decision Algorithm

When both conditions are true, the calendar switches to the next month. If either fails, the month is extended to 30 days.

In pseudocode:

If (Conjunction_Time < Sunset_Time) AND (Moonset_Time > Sunset_Time):
    Next_Day = 1st of New Month
Else:
    Current_Month = 30 Days
    Next_Day after = 1st of New Month

This guarantees that:

• No month starts before a new lunar cycle has actually begun.

• Every month has either 29 or 30 days — never shorter or longer.

• The entire year remains synchronized with the actual lunar cycle.

Example Calculation (Easy to Follow)

Let’s say today is the 29th of Sha‘ban in Mecca:

• Conjunction Time: 09:05 AM

• Sunset Time: 06:45 PM

• Moonset Time: 07:03 PM

Since conjunction is before sunset and the Moon sets after the Sun, both conditions are satisfied. Therefore, tomorrow becomes the 1st of Ramadan in the Umm al-Qura calendar.

But if conjunction had been at 07:30 PM (after sunset) or the Moon had set at 06:40 PM (before sunset), the month would be extended to 30 days, and the 1st of Ramadan would begin the following day.

Advantages of This Methodology

• Scientific Accuracy: Tied to actual lunar conjunctions and geometric conditions, not guesswork.

• Predictability: Dates can be calculated and published years in advance.

• Uniformity: Everyone in the country — from ministries to schools — follows the same dates.

• Balanced Approach: Uses astronomy but still respects Islamic principles of lunar month timing.

Difference from Other Hijri Calendars

Traditional Moon-Sighting

• Relies on actual human observation of the crescent.

• Subject to weather, horizon visibility, and observer experience.

• May result in different start dates across cities or countries.

Tabular Hijri Calendar

• Follows a fixed 30-year arithmetic cycle (19 years of 354 days, 11 leap years of 355 days).

• Easy to compute but sometimes 1–2 days off from the actual lunar phases.

Umm al-Qura Calendar

• Uses real astronomical data and a deterministic formula.

• Matches celestial events closely, yet is fully predictable.

• Provides a single official calendar for the entire nation.

Civil vs. Religious Use

It’s important to remember that the Umm al-Qura calendar is primarily a civil calendar. Religious observances such asRamadan, Eid al-Fitr, and Eid al-Adha are sometimes confirmed by official moon-sighting committees. This means in rare cases, the religious announcement may shift by one day from the pre-calculated date — a normal and expected part of the process.

Practical Uses for Visitors and Developers

• Schools & Universities: Plan academic calendars, exams, and holidays without waiting for last-minute updates.

• Government & Businesses: Set payrolls, contract dates, and deadlines confidently.

• Travelers & Pilgrims: Plan Hajj and Umrah with clear timelines, then verify final dates closer to travel.

• Websites & Apps: Use official implementations like .NET UmAlQuraCalendar or islamic-umalqura in ICU/CLDR for accurate date conversion.

• Researchers & Educators: Teach astronomy, lunar cycles, and Islamic calendar rules with a predictable dataset.

Key Takeaways

1. Two Golden Rules: Conjunction must occur before sunset, and moonset must happen after sunset in Mecca.

2. Perfect for Civil Use: Reliable for administration, software development, academic schedules, and public planning.

3. Religious Confirmation Still Matters: Always check official announcements for Ramadan, Eid, and Hajj before making religious decisions.

By understanding how the Umm al-Qura calendar works, you can use it confidently for planning, education, and development — while still respecting local moon-sighting practices where they apply.