Hijri year is the year Calendar era used in the Islamic calendar. The word Hijri derived from Hijrah. Hijrah is the emigration time of Prophet Muhammad (SM) from Macca to Madina in 622 AD. Counting of the 1st Hijri year was started on 622AD, after the Hijrah of Muhammad (SM) to Madina from Macca.
This is to be noted that the Hijri months must be started counting after seeing the 1st crescent of each lunar rotation, approximately 29 or 30 days but not more than 30 days. It means, if the moon is not visible due to cloud or any other reason, the new month cannot be started counting. However, if the month crosses 30 days, new month will start regardless of the sight of the moon.
The name of the 1st month of Hijri year is Muharram.