Caliph Umar, Started the Muslim Calendar, 639 CE
From English Alsadiqin
In 639 CE, Caliph 'Umar I started the Muslim calendar counting it from the lunar month, Muharram, in the year of the Prophet's migration to Medina, 16 July in 622 CE.
Sheikh Abdel-Rahman El-Gabarti (d. 1825), the greatest known chronicler of late 18th- and early 19th-century Egypt, recounted that Umar Ibn Al-Khattab was the first "setter of dates" of the Islamic era. According to his account, Abu Moussa Al-Ash'ari wrote to Umar Ibn Al-Khattab in distress: "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'bans is meant: is it the month that has passed, or that which is to come?" Umar is then said to have gathered the Companions of the Prophet and told them: "Money is flowing in, and what we have apportioned bears no date. How are we to reach a way of regulating this matter?"
Al-Hurmuzan -- taken as a prisoner of war when the Muslims conquered Persia, and converted to Islam at Umar's hands -- then replied: "The Persians have a system of tabulation known as mah ruz, and they base it on the victories of their kings." According to Al-Hurmuzan, "the word was thereafter Arabised as 'murakh', of which the root is 'tarikh' (history)." Umar then requested that the assembled notables "create a history for the people, that they may carry out their transactions by it, and that their dealings be accurately timed." Some of those who had gathered were Jewish converts to Islam, and they told him: "We have a system of tabulation like him, which is based on Alexander [the Great]." The others, however, were not satisfied, finding this system too lengthy [too far back]; one group suggested that the Persian history be followed. Others argued: "Their dates are not based on any specific beginning; whenever one of them became king, their history began again, and they discounted what had gone before." The assembly eventually agreed that Islamic history would begin with the Prophet's Flight, because none of those present disagreed on the date of that event, whereas that of the Prophet's birth, and when exactly he had received the first Divine message, aroused some controversy."
There are no such differences of opinion with regard to the date of the Hijra as there are with regard to the time when the call first came to Muhammad and with regard to the day and year of his birth. And although the date of his death is fixed, it is no pleasant thought to use (such a sad event) as the beginning of the era. The Hijra, moreover, coincided in time with the success of the religion (millah) of Islam, the frequent arrival of embassies, and the Muslim ascent to Power. It is a time of blessings and a very impressive (historical) event. The Hijra took place on Tuesday, Rabi 1, 8th. The first of that year -that is, al-Muharram-fell on a Thursday according to the average (calculation). After this had become generally known, it was considered (the correct date). However, according to observation (of the new moon) and astronomical(?) calculation, the day fell on a Friday. The author of the Nihayat al-idrak said that (the Hijra) was used, and for all future times the era was counted from it. Agreement on this matter was reached in the year 17 of the Hijra, the fourth year of the caliphate of 'Umar. Until then, each year (after the Hijra) was called after its main event, and this was used for dating purposes. The first year of the Prophet's residence in Medina was thus called: 'The permission to travel'. The second year was called: 'The year of the command to fight'. The third year: 'The year of the test', and so on. Afterwards, the custom of naming the year after the main events was abandoned.
When the need for toning up the administration of the Caliphate arose during the time of 'Umar ibn al-Khattab and it became necessary to have a calendar so as to fix the dates. The Caliph, who was so well aware of the sunna of the Prophet and of his temperament, instead of fixing the standard from the birth of the Prophet, which heralded an entirely new chapter in the history of man or his death which had placed such a heavy responsibility upon the shoulders of the Caliphs or some other event, he ordered the adoption of the Hijra as the basic date for the Islamic calendar.
Al-Hakim narrates the tradition on the authority of Ibn Shihab al-Zuhri that when the Prophet came to Medina, he ordered the introduction of the Muslim era, but this tradition has been held to be weak in authority by the Muhaddithun. The authoritative tradition, according to them, says that the custom of imprinting dates upon deeds, documents and epistles was given currency to during the time of the second Caliph according to the instructions left by the Prophet himself. (F. Rosenthal, A History of Muslim Historiography, Leiden 1952, p.309.).
Table: Showing base of Islamic Calendar selected by 'Umar to be 358 CE. When the Islamic Calendar matches Jewish Intercalculated Calendar
Shams al-Din Muhammad ibn 'Abd al-Rahman al-Sakhawi (d. 902) in his al-I'lan bi'l-Tawbikh li-man dhamma ahl al-tawrikh gives the following details about the origin of the Islamic calendar: "A report on the authority of Ibn 'Abbas states that there existed no era in Medina when the Prophet arrived there. People came to use an era a month or two after his arrival. This continued until Muhammad's death. Then, the use of an era was discontinued, and there was none during the caliphate of Abu Bakr and the first four years of the caliphate of 'Umar. Then, the (Muslim) era was established.” Umar is reported to have said to the assembled dignitaries among the men around Muhammad: "The income is considerable. What we have distributed has been without fixed dates. How can we remedy that?" One answer came from al-Hurmuzan. He had been king of alAhwaz. After his capture during the conquest of Persia, he had been brought to 'Umar and had become a Muslim. He said: "The Persians have a (method of) calculation which they call mahroz and which they ascribe to their Sassanid rulers. The word mahroz was arabicized as mu'arrakh, and the infinitive ta'rikh was formed from it.
'Umar chose the strictly lunar calendar as the official calendar, and no intercalation is permitted. This calendar had been kept by a minority of Arabs and had been in progress according to the lunar cycle since 358 CE, see Table 9.
The religious observances, thus perpetuated by Qussai, were in substance the same as in the time of the Prophet, and with some modifications by 'Umar are the same as we still find practiced at the present day. The grand centre of the religion was the Ka'aba; to visit which, to kiss the black stone, and to make seven circuits round the sacred edifice, was at all times regarded as a holy privilege. The result is essentially the same Islamic Calendar that is in use today.