Gregorian vs Hijri Calendar

How the Hijri Calendar Works

The Islamic (Hijri) calendar is a purely lunar calendar consisting of 12 months, each beginning with the sighting of the new crescent moon. Because a lunar year is roughly 354 days — about 11 days shorter than the Gregorian solar year — Islamic dates rotate through all seasons over a 33-year cycle. The calendar does not add a "leap month" to correct the drift, unlike the Hebrew lunisolar calendar. This means Ramadan, Hajj, and every Islamic occasion gradually moves earlier each Gregorian year. The Hijri year is abbreviated AH (Anno Hegirae — "In the year of the Hijra").

The Twelve Islamic Months

The twelve months of the Hijri calendar are: Muharram (sacred), Safar, Rabi al-Awwal (birth month of the Prophet), Rabi al-Thani, Jumada al-Awwal, Jumada al-Thani, Rajab (sacred), Sha'ban, Ramadan (the month of fasting), Shawwal (Eid al-Fitr falls on its 1st), Dhul Qa'dah (sacred), and Dhul Hijjah (Eid al-Adha on its 10th; Hajj during 8th–13th). Four months are sacred (Muharram, Rajab, Dhul Qa'dah, Dhul Hijjah) — in these months, fighting was traditionally forbidden, as mentioned in the Quran (9:36).

Why the Calendar Starts from the Hijra

The Hijri calendar epoch — year 1 AH — corresponds to the Prophet Muhammad's migration (Hijra) from Mecca to Medina in 622 CE. This date was chosen by the Caliph Umar ibn al-Khattab (may Allah be pleased with him) after consultation with the Companions, who agreed that the Hijra represented the true founding moment of the Muslim community — a transition from persecution to the establishment of an Islamic state. Dates before the Hijra are denoted BH (Before Hijra). The Prophet was born approximately 53 years before the Hijra (53 BH), and the Quran was first revealed approximately 13 years before it.

Key Islamic Dates in the Hijri Year

Every Hijri year contains several significant dates that Muslims observe worldwide: 1 Muharram — Islamic New Year; 10 Muharram (Ashura) — commemorated with fasting, especially by Sunni Muslims following the Prophet's practice of fasting this day; 12 Rabi al-Awwal — widely observed as the Mawlid (birthday) of the Prophet, though scholarly opinion on its celebration differs; 27 Rajab — associated with the Night Journey (Isra' and Mi'raj); 15 Sha'ban — Laylat al-Bara'ah (Night of Forgiveness) in some traditions; 1–29/30 Ramadan — the month of fasting; 1 Shawwal — Eid al-Fitr; 9 Dhul Hijjah — the Day of Arafah (fasting this day expiates two years of sins, per hadith); 10 Dhul Hijjah — Eid al-Adha.