Question 1

Why might the calculated Hijri date differ by one day from actual local observance?

Accepted Answer

The religious Islamic calendar is determined by confirmed visual sightings (Ru'yah) of the new crescent moon by national authorities like Egypt's Dar al-Ifta and the Saudi Supreme Court. Computational algorithms such as Intl.DateTimeFormat rely on predetermined astronomical tables (the Umm al-Qura system). Variations of ±1 day can occur depending on atmospheric conditions and verified regional sightings.

Question 2

What is the Umm al-Qura calendar standard utilized in software algorithms?

Accepted Answer

The Umm al-Qura calendar is the official astronomical lunar calendar developed by King Abdulaziz City for Science and Technology (KACST). A new lunar month begins if the astronomical conjunction (moon-earth-sun alignment) occurs prior to sunset and the moon sets after the sun at the coordinates of Mecca. It is standardized globally across modern operating systems under the 'islamic-umalqura' Unicode identifier.

Question 3

What are the four Sacred Months (Al-Ashhur Al-Hurum) in the Islamic lunar calendar?

Accepted Answer

Explicitly designated in the Quran (Surah At-Tawbah, verse 36), the four sacred months are three consecutive months: Dhu al-Qi'dah, Dhu al-Hijjah, and Muharram, and one individual month: Rajab. These months hold heightened spiritual gravity where good deeds are amplified and injustice is particularly grave.

Question 4

How does Hijri date conversion support accurate Zakat accounting?

Accepted Answer

The classical Sharia benchmark for the Hawl (wealth holding period) is exactly one lunar year (354 days). Translating financial events into the Hijri calendar enables individuals and treasury managers to establish an unshifting annual Islamic anniversary (such as the 1st of Muharram or 15th of Ramadan) to calculate Zakat at the 2.50% lunar rate.

Question 5

Why is the Hijri lunar year shorter than the Gregorian solar calendar?

Accepted Answer

The Gregorian calendar tracks the Earth's orbit around the Sun (approximately 365.2425 days), whereas the Hijri calendar follows twelve lunar synodic cycles (averaging 354.367 days). Consequently, the Islamic calendar is 10 to 12 days shorter each year, causing Islamic events and fasts to cycle through all four terrestrial seasons roughly every 33 solar years.

Question 6

Can this conversion utility process historical dates dating back to the Prophetic era?

Accepted Answer

Yes. The algorithm handles dates extending back to the beginning of the Islamic epoch in 1 AH (corresponding to 622 CE), applying backward astronomical synchronization to map early Islamic historical chronicles accurately.

No.	Month Name	Religious Status	Significant Observances
1	Muharram	Sacred Month (Hurum)	Islamic New Year, Day of Ashura (10th)
2	Safar	Standard	Second lunar month
3	Rabi' al-Awwal	Standard	Mawlid al-Nabi (Prophet's Birthday - 12th)
4	Rabi' al-Thani	Standard	Fourth month
5	Jumada al-Awwal	Standard	Fifth month
6	Jumada al-Thani	Standard	Sixth month
7	Rajab	Sacred Month (Individual)	Isra and Mi'raj (27th Rajab)
8	Sha'ban	Standard	Night of Mid-Sha'ban (15th)
9	Ramadan	Month of Fasting	Fasting obligation, Laylat al-Qadr, Quran revelation
10	Shawwal	Pilgrimage Month	Eid al-Fitr (1st Shawwal), Six days voluntary fasting
11	Dhu al-Qi'dah	Sacred Month (Hurum)	Eleventh month, assembly for Hajj journeys
12	Dhu al-Hijjah	Sacred Month (Hurum)	Hajj pilgrimage rites, Day of Arafah (9th), Eid al-Adha (10th)

Hijri to Gregorian Date Converter

The Islamic Lunar Calendar: Astronomical Modeling and Sharia Moon-Sighting

Overview of the Twelve Hijri Months and Major Observances

Three Verified Practical Date Conversion Case Studies

Scenario 1: Converting the Millennium Milestone (January 1, 2000 CE)

Scenario 2: Converting Historic Egyptian Revolution Day (July 23, 1952 CE)

Scenario 3: Establishing Hawl Anniversary for Liquid Wealth Zakat

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