Hazrat Mahdi (as) will not be known when he first appears

Imam Rabbani has stated that the coming of Hazrat Mahdi (as)WILL BE AT THE BEGINNING OF THE CENTURY, and that this appearance had not taken place even though 18 years had passed since the beginning of the century in his time: 

But this birth is not that which will appear at the coming of the Mahdi (as). THAT IS BECAUSE HIS APPEARANCE WILL BE AT THE BEGINNING OF THE CENTURY.Eighteen years have currently gone by since the beginning of the century. (Imam Rabbani, Letters of Rabbani, Letter no 381, p. 1184)

Imam Rabbani’s reference to “HIS APPEARANCE WILL BE AT THE BEGINNING OF THE CENTURY” MEANS THAT THE PORTENTS OF THE COMING OF HAZRAT MAHDI (AS) WILL BEGIN TAKING PLACE AROUND THE BEGINNING OF THE CENTURY. IT DOES NOT MEAN THAT Hazrat Mahdi (as) will appear immediately at the beginning of the century, that Islamic moral values will prevail at once and that Hazrat Mahdi (as) will be recognized by people as soon as he appears.

As Imam Rabbani says, JUST ABOUT ALL THE PORTENTS OF THE COMING OF HAZRAT MAHDI (AS) OF WHICH OUR PROPHET (SAAS) SPEAKS HAVE HAPPENED IN THE 30 YEARS BETWEEN THE YEAR 1400 AND THE PRESENT (These portents are explained in the coming parts of the book).

Imam Rabbani’s use of the term “EIGHTEEN YEARS HAVE CURRENTLY GONE BY SINCE THE BEGINNING OF THE CENTURY”is most significant. With these words, Imam Rabbani indicates that had Hazrat Mahdi (as) appeared, he would himself, as a person of knowledge and foresight, have felt and realized Hazrat Mahdi (as) through the luminosity of his faith from the fact that the portents of his coming having taken place during the 18 years since the beginning of the century. The fact is, however, although 18 years had gone by since the beginning of the century on Imam Rabbani’s time, the portents of the coming of Hazrat Mahdi (as) had not taken place, for which reason he had not yet appeared.

Therefore,Imam Rabbani is not saying or implying that Islamic values will prevail the world as soon as Hazrat Mahdi (as) appears and that Hazrat Mahdi (as) will therefore be recognized by everyone that sees him. But he notes that wali (saint) people like him possessed of profound knowledge will be able to recognize Hazrat Mahdi (as).

It can also be seen from statements by Said Nursi that not everyone will recognize Hazrat Mahdi (as) when he first appears, that he will not be known despite being among the people, and that ONLY PEOPLE WITH KNOWLEDGE AND FORESIGHT WILL BE ABLE TO RECOGNIZE HIM FROM THE RADIANCE OF HIS FAITH, THE PROFUNDITY OF HIS FAITH AND THE MAJESTY OF HIS FAITH: 

However, as we said, this world is the arena of trial. The door is opened to the reason, but the will is not taken away. SO, WHEN THOSE INDIVIDUALS [Hazrat Mahdi (as) and the Prophet Jesus (as)], and even the terrible antichrist, APPEAR, MANY PEOPLE AND HIMSELF EVEN WILL NOT KNOW TO START WITH THAT HE IS THE ANTICHRIST. THOSE INDIVIDUALS OF THE END TIMES [HAZRAT MAHDI (as) and THE PROPHET JESUS (as)] WILL BE KNOWN THROUGH INSIGHT AND THE LIGHT OF BELIEF. (Bediuzzaman Said Nursi, Words / Twenty-Fourth Word - Third Branch - pp. 354-355) 

Bediuzzaman Said Nursi, like Imam Rabbani someone possessed of knowledge and foresight, stated in his Letters that the Prophet Jesus (as) will not be recognized by everyone when he returns, and that HE WILL ONLY BE RECOGNIZED BY STUDENTS OF DEEP FAITH AROUND HIM, BY THE LUMINOSITY OF HIS FAITH:   

... WHEN JESUS (AS) COMES, it is not necessary that EVERYONE SHOULD KNOW HIM TO BE THE TRUE JESUS (AS). His elect and those close to him (his close followers with deep faith) will recognize him through the light of belief. It will not be self-evident so that EVERYONE WILL NOT RECOGNIZE HIM. (Bediuzzaman Said Nursi, Letters, Fifteenth Letter)  

NEITHERIMAM RABBANI’S WORDS NOR THE DESCRIPTIONS GIVEN BY SAID NURSI MEAN THAT THE MORAL VALUES OF ISLAM WILL PREVAIL THE WORLD AS SOON AS HAZRAT MAHDI (AS) APPEARS OR THAT HAZRAT MAHDI (AS) WILL IMMEDIATELY BE RECOGNIZED BY EVERYONE.If the moral values of Islam were to prevail across the world as soon as Hazrat Mahdi (as) appears, then everyone would immediately recognize and identify him. Hazrat Mahdi (as) would not then encounter any difficulties under such circumstances. The fact is that the hadith of our Prophet (saas) unequivocally state that Hazrat Mahdi (as) will not be recognized by the public and that he will resemble the Prophet Joseph (as) in that regard, that he will face difficulties and pressure and that he will be exposed to all kinds of danger, such as murder, like the Prophet Moses (as), difficulties and pressure, conspiracies, imprisonment and exile, and that he will live in occultation:  

... THEN HAZRAT MAHDI (AS) RESEMBLES THE PROPHET JOSEPH (AS), AND PEOPLE WILL SEE HIM [HAZRAT MAHDI (AS)] BUT WILL NOT SEE THAT HE IS HIM [HAZRAT MAHDI (AS)] AND IT IS CERTAIN, as Hazrat Ali has said, HE WILL NOT BE SEEN UNTIL THERE COMES A PROCLAMATION FROM THE SKY.(Sheikh Muhammad ibn Ibrahim Numani, al-Ghaybah al-Numani p. 167) 

Abu Bashir says: I heard Imam Muhammad Baqr (as) say: "HE WHO POSSESSES THIS MYSTERY [HAZRAT MAHDI (AS)] WILL HAVE THE SUNNAH OF FOUR PROPHETS… I SAID, WHAT IS THE SUNNAH OF JOSEPH (AS)? AND HE SAID: IMPRISONMENT AND OCCULTATION. (Sheikh Muhammad ibn Ibrahim Numani, al-Ghaybah al-Numani, p. 191) 

Imam Zayn al-Abidin stated:"There are some similarities between our Qaim [Hazrat Mahdi (as)] and Allah's Messengers. He has similarities to each one of the Prophets Noah (as), Abraham (as), Moses (as), Jesus (as), Job (as) and Muhammad (saas). He has similarity to NOAH (as) in having a long life; to ABRAHAM (as) in having his birth being hidden and his staying away from the public; TO MOSES (AS) IN HIS STATE OF FEAR(THE INTENSITY OF DANGERS DIRECTED TO HAZRAT MAHDI (AS); HIS BEING FACE TO FACE TO ALL KINDS OF DANGER LIKE MURDER, PLOTTING, ARREST, TAKING INTO CUSTODY AND EXILE) AND HIS CONSTANTLY SPENDING HIS LIFE IN OCCULTATION; to Jesus (as) in people being in conflict about him (some people will say Hazrat Mahdi (as) will come while others will say he will not); to Job (as) in being delivered to salvation after trouble (Hazrat Mahdi (as) will also suffer many difficulties, oppression and trouble; however just like the Prophet Job (as) he will be saved by Allah's mercy); to Muhammad (saas) in his appearing with his sword [our Prophet's (saas) holy relics which are his sword, standard and mantle will be with Hazrat Mahdi (as)]. (Sheikh al-Saduq, Kamal al-Din, p. 322, Section 31, Hadith number 3) 

Sadr al-Sayrafi says: I heard Imam Abu Abdullah Jafar Sadiq say: He said: "THE OWNER OF THIS TASK [THE HAZRAT MAHDI (AS)] WILL HAVE A RESEMBLENCE TO JOSEPH (AS)]." AND I SAID: "IT IS AS IF YOU ARE TELLING US OF AN OCCULTATON OR ASTONISHMENT." (Sheikh Muhammad ibn Ibrahim Numani, al-Ghaybah al-Numani p. 189)