Historically speaking, amongst the laity, what was famous regarding the martyrdom of Fāṭimah (s) was the First Fāṭimīyyah – meaning 13th Jamādī al-Awwal. However, lately, the Second Fāṭmīyyah – meaning 3rd Jamādī al-Thānīyah has become popular. Perhaps the origin of this popularity goes back to Ḥājī Nūrī (d. 1902) or his students. The reason they have mentioned is that the number 75 in the various manuscripts was an alteration of the number 95. Such an alteration between the words sab’īn (سبعین) and tis’īn (تسعین) is very well-known and I do not recall an instance where I came across these words in a book of history and that there was no mistake in the different manuscripts on these two words. In the various manuscripts of historical works, they would mistake and confuse the number sab’īn with tis’īn or vice-versa all the time. Since experience shows mistakes occur in these two specific words, we cannot apply the principle of absence of error in this instance.
In any case, whatever day the martyrdom of the lady (s) happens to be, one must make the intention of rajā’ (hope) and as per the narrations, they will get the same reward as has been promised due to their intention of rajā’. In al-Maḥāsin of Barqī a tradition from Imam Bāqir (a) says, do not reject a narration transmitted by the Ḥarūrīyyah – who were from the Khawārij – because it is possible for such a narration to have been uttered. It is not most definitely false, and since it has the likelihood of being authentic, safeguard it with the hope that it is. This is what the principle of leniency and its like also imply.1
As per the traditions, the promise of reward has been given for seeking nearness to her and hence should be observed albeit the first Fāṭimīyyah or the second.
I heard from Aqā Mīrza Jafar Shīrāzī – from Tabrīz – regarding the knowledge of the Imams, he said: at times the knowledge of something can be perfection, while other times the ignorance of something can be perfection and Allah would take knowledge away from the Imams (a) in those later cases. For example, the night when Imam Ali (a) slept on the bed of the Prophet (p), if he had known that sleeping on the bed will not result in any harm, this would not have been an instance of perfection. The condition of perfection which was exhibited through the sacrifice of the Imam (a) is that he should not know, and he did not know. In cases where ignorance is a condition of acquiring perfection, Allah (swt) takes away the knowledge.
On the night of Qadr and its like, not knowing has a benefit and the Imams (a) themselves have not mentioned the details. In the case of the grave of Zahrā (s) and the days of her martyrdom, not knowing has a benefit, as it is a sign of her oppression. The signs and evidence must remain and should not disappear; the Black Stone and other things are signs and evidence which continue to remain, and one of the signs and evidence is the issue of her (s) grave being in an unknown location.
Source: Dars Khārij of Āyatullah Sayyid Shubayrī Zanjāni, 23rd September 1995