When Did The Islamic Calendar Begin. In the year 639, caliph umar i created a lunar calendar starting with july 16, 622. It is one of the four sanctified months about which the holy quran says, the number of the months according to allah is twelve months.

The beginning of the islamic calendar is established in the year 638 of the gregorian calendar, at the time of caliph ‘umar b. The islamic calendar begins with one of the most iconic events in islamic history;