The year the Hijri calendar was introduced
17-1-2015 | IslamWeb
Question:
Which year starting hijara calebdar
Answer:
All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.
The use of the Hijri calendar began in 17 AH during the Caliphate of ‘Umar 
; he was the first to chronicle in Hijri year. Ibn Hajar 
said in Fat-h Al-Baari:
"Abu Nu‘aym Al-Fadhl ibn Dakeen narrated it in his Taareekh, and also Al-Haakim reported it from him on the authority of Ash-Sha‘bi that Abu Moosa wrote to ‘Umar that letters come from him (‘Umar) without date, so ‘Umar gathered the people (to consult them about this), so some of them said that they should start numbering with the date when Muhammad 
was commissioned as a Prophet, and some of them said that they should start with the Hijrah (the Prophet's immigration from Makkah to Madeenah). ‘Umar said: We will start with the Hijrah as it separated Truth from falsehood. So, they started numbering with it, and when they agreed on this, some of them said that they should start with the month of Ramadan, and ‘Umar said: Rather, we will start with the month of Muharram as this is the month when the pilgrims go back to their hometowns after completing their ritual of Hajj; so they agreed on it." [End of quote]