The hijri Calendar is a lunar based Calendar. It consists of 12 months, and the beginning of each month is determined by the sighting of a new moon. It used to mark important events for Muslims such as the month of fasting, the month of the Holy pilgrimage, Hajj, etc.

The Calendar was found 17 years after Prophet Muhammad’s ﷺ emigration (Hijrah) from Mecca to Madina with 70 other Muslims, thus called Hijri.

Established in the 637/638 AD by Umar Ibn Khattab ‎رضي الله عنه , the second caliph, the Calendar was found 17 years after Prophet Muhammad’s ﷺ emigration (Hijrah) from Mecca to Madina with 70 other Muslims. Umar ‎رضي الله عنه realised the need of having their own Islamic Calendar and system of signifying dates and important events for the Muslims.

The lunar calendar is based on astronomical calculations with each year adding up to about 354.37 days, while in the Hijri Calendar start of each month is based on the sighting of the moon.