As Salaamu Alaiekum Wa Rahmatul Laahi Wa Barakaatuhu,
In the time of Hazrat Ameer ul Mumineen Hazrat ‘Umar (Farooq-e-A’zam) (Radiyal Laahu ‘Anhu) officially established the Islaamic Hijri Calendar. It is a co-incidence that the first date of Islaamic year (first Muharram) is attached with his remembrance, the date of his martyrdom. His era after our Beloved Holy Prophet (Sallal Laahu ‘Alaiehi Wa Sallam) was the golden period of Islaamic history. He was the conqueror of forty four countries only within the span of ten years.