How can the controversy about the date of birth of Imam Mahdi (may Allah hasten his return), which some say corresponds to the number of the letters of the word نور (“nur,” light) – 256 – while according to some traditions, it took place in the year 255 A.H., be explained. In what year did the occultation of that personage take place?
Dispute about such matters does not harm the basic topic or cause an enigma.
Such disagreement exists with regard to the date of birth of most historical personalities; in fact in many cases their dates of birth and death are unknown.
The disagreement about the date of birth of Imam Sahib al-‘Amr (may Allah hasten his return) is less than the disagreement existing about the date of birth of some of the Imams and the Prophet (peace be upon him and his family) himself.
The reliable opinion is 255 A.H., which Fadl ibn Sha¤han al-Nayshapuri—who is one of the major traditionists and a contemporary of Imam Hasan al-‘Askari (peace be upon him) - has related, and his intermediary is a person like Muhammad ibn ‘Ali ibn Hamza ibn Husayn ibn ‘Ubaydullah ibn ‘Abbas ibn ‘Ali ibn Abi Talib (peace be upon him).
As for the occultation of Imam Sahib al-‘Amr (may Allah hasten his return):
From the very time of birth the public did not have permission to visit him in the usual manner, and his venerable father would only grant special companions and Shi‘a the felicity of visiting his peerless son and كلمة الله باقية (Allah’s remaining word). The commencement of the minor occultation, which was also the beginning of that personage’s Imamah, took place on the day of martyrdom of Imam Hasan al-‘Askari (peace be upon him), that is in the year 260 A.H.
A point which must be mentioned here is that the coming up of the issue of the occultation of the Imam was not unexpected for the Shi‘a and believers in Imamah when it occurred, since it had been referred to before that time in many traditions, and the people knew that Imam Sahib al-‘Amr (may Allah hasten his return) will have to occultations—a short occultation called “sughra” and “qusra” and a long occultation called “kubra” and “tula”.
The detailed report of that has been mentioned completely in the books and usul (books of principles) of the Shi‘a which were written before the birth of Imam Sahib al-Zaman (may Allah hasten his return).