Mujaddid's of Islam
A Mujaddid is a pious person who revives an rejuvenates the faith of Islam in each century, in much the same way as the previous series of Hebrew Prophets did.
"Verily, God will raise for this community, at the beginning of every century, one who will renovate the religion." (Abu Daud, Hadith)
They tend to be the most among great saints and scholars who acted to prevent false and erroneous beliefs entering Islam. There is only one Mujaddid in each century although there are differences as to whom should be included. So, in a particular century there may be two candidates (one in the east and one in the west).
Century.......name.................Muslim Era.....Christian Era