Saying that Hazrat Mahdi (as) will appear at the beginning of the Hijri 1400s does not mean that he will be recognized as soon as he appears

Since we are now in Hijri 1430, 30 years have passed since the Hijri date provided by our Prophet (saas). In other words, as al-Barzanji describes, there are at least another 10 years until Hazrat Mahdi (as) is recognized and until his spiritual and intellectual dominion over the world.

The way that some people suggest, on the basis of no reliable evidence and no hadiths, that “Hazrat Mahdi (as) will be immediately recognized as of Hijri 1400, and everyone will at once know that he is Hazrat Mahdi (as)” is a complete contravention of the ideas of Sunni scholars. Anyone making such a claim is opposing the belief of the Ahl al-Sunnah. That is because, for instance, the great Sunni scholar Al-Barzanji made this statement about the time needed for Hazrat Mahdi (as) to be recognized following his appearance:

(The following extract is from page 301 of the 10th Turkish edition of Muhammad Ibn Rasul al-Hussain al-Barzanji’s Al-Isha'ah li-ashrat al-sa'ah translated into Turkish by Naim Erdogan.)

FOUR, FIVE OR EVEN TEN YEARS ARE REGARDED AS THE FIRST YEARS OF THE CENTURY. ACCORDINGLY, THAT HAZRAT MAHDI (AS) WILL APPEAR SEVEN, NINE OR THIRTY YEARS BEFORE THE HUNDREDTH YEAR IS NO OBSTACLE TO HIS COMING AT THE BEGINNING OF THE CENTURY... THE SAME APPLIES IF HIS APPEARANCE IS AFTER THAT PERIOD. (Al-Barzanji, Al-Isha'ah li-ashrat al-sa'ah, p. 301)

Al-Barzanji thus states that even 4, 5 or 10 years after the year 1400 according to the Islamic calendar can be accepted as the early 1400s. Indeed, as Imam Rabbani says;

AT THE HEAD OF EACH CENTURY, ALLAH SENDS A MUJADDID among the scholars of this community who revives the Law of Allah [the essence of Qur'anic moral values and the Sunnah of our Prophet (saas)]. (Imam Rabbani, Letters of Rabbani, 1/520)

That HAZRAT MAHDI (AS) WILL BE RECOGNIZED 7, 9 OR EVEN 30 YEARS BEFORE OR AFTER THE HIJRI YEAR 1400 is no obstacle to his coming in the year 1400. Even if these situations do prevail Hazrat Mahdi (as) will still have emerged at the beginning of Hijri 1400.

This statement by Al-Barzanji, a reliable Sunni scholar, is an exceedingly significant reply to those to seek to cover up, shroud or conceal the coming of Hazrat Mahdi (as) by making irrational and illogical claims along the lines of "Since Hazrat Mahdi (as) was not immediately identified by people in Hijri 1400, he has not appeared, and although 30 years have passed since Hijri 1400 the great portents have still not come about, meaning that Hazrat Mahdi (as) will not be coming in this century but will happen in some other century…” Even if Hazrat Mahdi (as) appears before Hijri 1400 or 7, 9 or 30 years after it, he is still the awaited Great Mahdi (as). By Allah’s leave, none of these cases can alter this truth revealed in trustworthy hadiths of our Prophet (saas).

(The caption below is the relevant section from pp. 88, 89 and 90 of Dr. Suat Arusan’s Turkish translation of Al-Muttaqi al-Hindi’s Al-Burhan fi Alamat al-Mahdi Akhir az-Zaman)