The Calendar Before Islam
Pre-Islamic Arabia used the lunisolar calendar which was based on the phases of the moon, as well as the seasons.
The Establishment of The Hijri Calendar by the second Caliph, Umar (May Allah ﷻ be pleased with him)
The hijri calendar was first established by Umar Ibn al-Khattab, in 637/638 AD.
Abu Musa al-Ash’ari wrote to Umar Ibn al-Khattab saying,
❝Letters have reached us from the Commander of the Faithful, but we do not know which to obey. We read a document dated [the month of] Sha’ban, but we do not know which of the Sha’ban is meant: is it the month that has passed, or that which is to come?❞
After consulting the Prophet’s ﷺ Companions, Umar Ibn al-Khattab decided that the year of the Prophet’s ﷺ immigration should become the beginning of the Islamic calendar. Hijra was the most important event in the Islamic world which brought about the Islamic nation, hence they named the new dating system the Hijri calendar.
Some of the companions wanted the calendar to start with the month of Ramadan, but Umar thought that Muharram is more appropriate to be the first month of the Hijri calendar as it is when the Hajj season is over.
One Hijri year is made up of 354 days, which is the time it takes for the moon to circle the Earth 12 times and each Lunar year advances 11 days from the previous one.
May the Hijrah of the Prophet ﷺ stay glorified in our minds and May the new year brings us nearer to Allah.