Hijri to Gregorian Date Converter

The Astronomical & Jurisprudential Guide to the Islamic Hijri Calendar

The Islamic calendar (known as the Hijri Calendar or al-Taqwim al-Hijri التقويم الهجري) is the liturgical and civil calendar utilized by over 1.9 billion Muslims across the globe to determine Islamic holy days, fasting during Ramadan, the annual Hajj pilgrimage to Mecca, Zakat calculation anniversaries (Hawl), and Islamic contractual dates. Designated by the suffix AH (Latin for Anno Hegirae, "in the year of the Hijra"), its inaugural epoch dates back to the historic migration of Prophet Muhammad (peace be upon him) from Mecca to Medina in 622 CE.

1. Pure Lunar Mechanics: Why the Islamic Year is 11 Days Shorter

Unlike the solar Gregorian calendar which tracks the Earth's 365.2425-day orbital revolution around the Sun, the Hijri calendar is strictly lunar (Qamari). Each month tracks the synodic lunar cycle—the period between one conjunction (new moon) and the next:

2. The Twelve Islamic Months & Their Spiritual Significance

The Holy Quran explicitly references the twelve months in Surah At-Tawbah (9:36): "Indeed, the number of months with Allah is twelve months in the register of Allah from the day He created the heavens and the earth; of these, four are sacred."

1. Muharram (مُحَرَّم): Sacred month. Marks the Islamic New Year. Contains the 10th of Muharram (Day of Ashura), a recommended day of fasting.
2. Safar (صَفَر): Second month. Historically associated with travel and trade caravans.
3. Rabi' al-Awwal (رَبِيع الأَوَّل): The third month, celebrated for the blessed birth of Prophet Muhammad (PBUH) on the 12th of Rabi' al-Awwal (Mawlid).
4. Rabi' al-Thani (رَبِيع الآخِر): The fourth month of the lunar calendar.
5. Jumada al-Awwal (جُمَادَى الأُولَى): The fifth month of the Islamic calendar.
6. Jumada al-Thani (جُمَادَى الآخِرَة): The sixth month of the Islamic calendar.
7. Rajab (رَجَب): Sacred month. Contains the 27th of Rajab, commemorating the miraculous Night Journey and Heavenly Ascension (Isra and Mi'raj).
8. Sha'ban (شَعْبَان): Eighth month. Serves as spiritual preparation for Ramadan. Includes Shab-e-Barat (15th of Sha'ban).
9. Ramadan (رَمَضَان): The ninth and holiest month. Obligatory daily fasting from dawn to sunset, recitation of the Holy Quran, and Laylat al-Qadr (the Night of Power).
10. Shawwal (شَوَّال): The tenth month. Opens with the celebration of Eid al-Fitr on the 1st of Shawwal, marking the joyful culmination of Ramadan fasting.
11. Dhul-Qi'dah (ذُو القَعْدَة): Sacred month. Month of peaceful travel and preparation for Hajj pilgrims.
12. Dhul-Hijjah (ذُو الحِجَّة): Sacred month. Host to the annual Hajj pilgrimage. Features the Day of Arafah (9th) and Eid al-Adha (10th).

3. Moonsighting (Ru'yat al-Hilal) vs. Astronomical Calculation

A frequent point of inquiry among users is why Islamic dates occasionally vary by 24 to 48 hours across different countries. There are two prevailing methodologies:

• The Astronomical Umm al-Qura Standard: Promulgated by the Institute of Astronomical & Geophysical Research in Riyadh, this civil calendar determines month beginnings based on whether the astronomical conjunction occurs before sunset at Mecca and whether moonset occurs after sunset. It provides an exact, predictable schedule for civil calendars.
• Traditional Visual Moonsighting (Ru'yat): Followed by Islamic jurisdictions in Pakistan (Ruet-e-Hilal Committee), India, Morocco, the UK, and North American moonsighting committees. Because the crescent moon must be visibly sighted locally by human observers, adverse weather or geographical lag can cause months to begin one day later than calculated tables.

Toolhast's converter provides an integrated Moon Sighting Offset slider (-2 to +2 days) so you can synchronize your dates precisely with your local mosque or regional Islamic authority.

4. Mathematical Conversion Algorithm (Julian Day Number)

To translate dates between solar and lunar systems with zero drift, astronomers employ the Julian Day Number (JDN)—a continuous count of days elapsed since January 1, 4713 BCE:

By combining classical astronomical JDN formulations with modern browser-native Umm al-Qura internationalization APIs, Toolhast executes all calculations locally on your device with sub-millisecond responsiveness.