The Islamic calendar is a lunar calendar meaning it is based on the movement of the moon. It has 12 months, 354 days in one year and 355 days in a leap year.

The Islamic calendar started when the Prophet Muhammad migrated from Makkah to Madina. In the Arabic language the meaning of emigration is Hijrat, because of this the Islamic calendar is also known as the Hijri calendar. The Hijri year is denoted by H or AH (AH = anno Hegirae in Latin).

The Hijri calendar is used in many Muslim countries, some use it as their official calendar but most only use it for religious purposes.