Islamic Calendar

The Islamic calendar, also known as the Hijri calendar, is a timekeeping system based on the lunar cycle. The year consists of 12 months, each lasting 29 or 30 days, determined by the moon's orbit between successive new moons.

A Hijri year is approximately 354 or 355 days, roughly 10 to 12 days shorter than the solar (Gregorian) year. For this reason, the Islamic months do not correspond to fixed seasons: Ramadan, for example, can fall in summer, autumn, or winter over the course of several years.

Beginning of the Era

The counting of years begins from the Hijra, the migration of the Prophet Muhammad and his companions from Mecca to Medina. That year was taken as the first year of the calendar. The system is believed to have been established under the second caliph, Umar ibn al-Khattab. Years are marked with the notation "H" (Hijri) or "AH".

Months

The months are: Muharram, Safar, Rabi' al-awwal, Rabi' al-thani, Jumada al-awwal, Jumada al-thani, Rajab, Sha'ban, Ramadan, Shawwal, Dhu al-Qi'dah, and Dhu al-Hijjah. Four months—Muharram, Rajab, Dhu al-Qi'dah, and Dhu al-Hijjah—are designated as sacred months.

How the Month Begins

Traditionally, a month begins when the new crescent moon is sighted by the naked eye in the evening after sunset. The new day begins at sunset, not at midnight. Some countries and organizations now use astronomical calculation to plan dates in advance. Differences between the observational and computational methods mean that the dates of Eid can vary from one country to another.

Current Use

The Hijri calendar is used to determine the times of worship: the start of Ramadan, Eid al-Fitr, the Hajj, and Eid al-Adha. Many Muslim-majority countries conduct daily administration using the Gregorian calendar, while the Hijri calendar is consulted for religious and cultural matters. Some countries, notably Saudi Arabia, formally used the Hijri calendar for state purposes for an extended period.