The Islamic calendar—known as the Hijri Calendar (At-Taqwim al-Hijri)—is purely lunar, governed by the natural monthly orbital cycles of the moon around the Earth. Established during the Caliphate of Sayyiduna Umar ibn al-Khattab (may Allah be pleased with him), the calendar marks its epoch from the historic Hijrah (migration) of the Prophet Muhammad (peace be upon him) from Makkah to Madinah in 622 CE.
The Divine Lunar System in the Quran
The lunar calendar is divinely appointed in the Holy Quran:
“Indeed, the number of months with Allah is twelve [lunar] months in the register of Allah [from] the day He created the heavens and the earth; of these, four are sacred.” (Surah At-Tawbah, 9:36).
Why the Islamic Year is 10 to 11 Days Shorter
A complete lunar month (synodic cycle) lasts approximately 29.53059 days. Consequently, an Islamic year of 12 lunar months consists of either 354 or 355 days, compared to the Gregorian solar year of 365.2425 days.
Because the lunar year is roughly 11 days shorter, Islamic months migrate through all four seasons over a 33-year astronomical cycle. This divine design ensures that no single region of the world permanently fasts during harsh summer days or freezing winter nights; worship is distributed with sublime fairness across all human generations.
The Twelve Hijri Months and Their Significance
- Muharram: One of the four sacred months; contains the day of Ashura.
- Safar: The second month of the Islamic year.
- Rabi’ al-Awwal: The blessed month of the birth of the Prophet Muhammad (peace be upon him).
- Rabi’ al-Thani: The fourth month.
- Jumada al-Ula: The fifth month.
- Jumada al-Thaniyah: The sixth month.
- Rajab: The second sacred month; associated with the miraculous Isra and Mi’raj.
- Sha’ban: The month of preparation for Ramadan containing Laylat al-Bara’at.
- Ramadan: The month of obligatory fasting, revelation of the Holy Quran, and Laylat al-Qadr.
- Shawwal: Commences with Eid-ul-Fitr and includes the recommended 6 days of Shawwal fasting.
- Dhu al-Qi’dah: The third sacred month; traditional time of embarking on the Hajj pilgrimage.
- Dhu al-Hijjah: The fourth sacred month; contains the first 10 blessed days, the Day of Arafah, and Eid-ul-Adha.
Moon Sighting Principles (Ru’yat al-Hilal)
The start of each Islamic month is determined by the sighting of the new crescent moon (Hilal) on the evening of the 29th day. The Prophet (peace be upon him) instructed: “Fast when you see it [the crescent], and break your fast when you see it; but if it is overcast, then complete the month of Sha’ban as thirty days” (Sahih al-Bukhari).
Because visibility depends on atmospheric conditions, cloud cover, and lunar crescent altitude, dates can vary by one day between countries. Salatify includes a configurable Hijri date offset adjustment (-2 to +2 days) so users can synchronize perfectly with their national moon-sighting committee.