A mujaddid (reviver) will come in every century

The great mujaddid of the End Times who will come in Hijri 1400 is Hazrat Mahdi (as)

It is revealed in the hadiths handed down from our Prophet (saas), in the work known as the Sunan Abu Dawud by Abu Dawud, in the hadiths included in Imam Rabbani’s Maktubat (Letters) and the Risale-i Nur Collection by Said Nursi, the mujaddid of the Hijri 1300s and the greatest scholar and mujaddid of the last 1000 years, that a person will come to rid Islam of innovations that have entered it subsequently and who will be instrumental in reviving the moral values and virtue of Islam and the Sunnah of our Prophet (saas). Our Prophet (saas) has given a date of Hijri 1400 for the appearance of Hazrat Mahdi (as) and said that people would start collecting around him as of then. Said Nursi also said that Hazrat Mahdi (as) would come one century after Hijri 1300 and will eliminate the system of oppression that rules the world at that time.

According to Abu Hurairah’s account, the Messenger of Allah (saas) said: Allah will raise for this community AT THE BEGINNING OF EVERY HUNDRED YEARS the one who will revive its religion for it. (Sunan Abu Dawud 5/100)

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)

ONCE IN EVERY CENTURY, ALLAH SENDS A MUJADDID [SOMEONE WHO REVIVES RELIGION]. (Bediuzzaman Said Nursi, Barla Addendum, p. 119)
Bediuzzaman states that the mujaddid of the 1200s was Mawlana Khalid.

Allah sends someone to revive the faith AT THE BEGINNING OF EVERY CENTURY, Mawlana is the mujaddid of the year 1200, in other words, of the 12th century. (Bediuzzaman Said Nursi, Barla Addendum, p. 120)

Mawlana Khalid al-Baghdadi was born in Hijri 1193 (1779 AD) and died in Hijri 1242 (1827 AD). The great majority of Muslim scholars are agreed that this blessed individual is the mujaddid between the 12th and 13th centuries (Hijri calendar).

Bediuzzaman Said Nursi Is the Mujaddid of the Hijri 1300s
Immediately after saying that Mawlana Khalid is the mujaddid of Hijri 1200, Bediuzzaman Said Nursi then states quite explicitly that he and his works serve as the mujaddid exactly one century later, in Hijri 1300:

Exactly AFTER A CENTURY, the parts of the RISALE-I NUR APPEAR ALL AROUND AND SERVE TO THE VERY SAME PURPOSE… With the meaning fortified by the clear expression of the hadith, it is our conviction that, in terms of reviving the religion, the Risale-i Nur is IN THE POSITION OF A MUJADDID. (Bediuzzaman Said Nursi, Barla Addendum, p. 121)