The History of the Hijri Calendar: Umar bin Khattab's Legacy Enduring 14 Centuries

Muslims worldwide have just entered the Islamic New Year 1448 Hijri. The Islamic calendar was officially instituted during the reign of Caliph Umar bin Khattab around the year 17 Hijri, or 638 CE.

Founder of Rumah Fiqih Indonesia, Ustadz Ahmad Sarwat, explained that humanity has long recognised two common calendar systems. The first is the solar system (syamsiyah), based on the Earth’s revolution around the sun. The second is the lunar system (qamariyah), which refers to the moon’s orbit around the Earth.

“Both of these calculation systems have existed for a long time, well before the sending of Prophet Muhammad SAW. The Arab and Jewish peoples used the lunar calendar calculation system, based on the moon’s orbit around the Earth,” wrote Ustadz Ahmad Sarwat, as quoted from the official Rumah Fiqih Indonesia website.

In this system, the length of a month is not always the same, but is sometimes 29 days and sometimes 30 days. A year consists of 12 months: Muharram, Safar, Rabiul Awwal, Rabiuts Tsani (Rabiul Akhir), Jumadil Awwal, Jumadits Tsani, Rajab, Sya’ban, Ramadhan, Syawal, Zulkaidah, and Zulhijjah.

Although this calendar system had long been known, pre-Islamic Arab society apparently did not yet recognise the numbering of years. They were accustomed to mentioning the date and the name of the month, but did not determine the year’s number.

According to Ustadz Sarwat, Arabs at that time could say that a day fell on 1 Muharram, but they did not know or did not establish the year.