Thread by @Simwal

BRIEF HISTORY OF ISLAMIC HIJRI CALENDAR
Short #Thread

The Islamic calendar was introduced by Amirul mu’mineen Umar bin Al Khattab (رضي الله عنه) the second Caliph of Islam in 17AH/638 AD.

The reason for introduction of the calendar was because of conflicting, dating systems being used during that time period. One narration is, a case was referred to Amirul Mu’mineen ‘Umar (رضي الله عنه ) concerning a contract that one man had with another

saying that what he owed him became due in Sha‘baan.
Umar said; Which Sha‘baan? The Sha‘baan of this year we are in now or of last year or of next year?

Another narration is, that Abu Musa Ash’aari, one of the officials of the Caliph Umar in Basrah, complained about the absence of any years on the correspondence he received from Umar, making it difficult for him to determine which instructions were most recent.

Umar (رضي الله عنه) summoned the Sahaabah and consulted them about adopting a calendar.
Some suggested adopting other calendars ( Persian and Byzantine), others suggested dating it from the birth of the Prophet (ﷺ) or from the beginning of his mission, or from his migration.

Umar (رضي الله عنه ) chose the date of the Hijrah ( migration ) to Madina because it was when the Islamic state was founded.
They agreed to make Muharram the first month. So the first day of the first month of the Islamic calendar (1 Muharram 1 AH) was Friday, 16 July 622AD.