The Mahdi ("Guided One") is a symbol of Shia and Sunni Islam who has been prophesied to appear at a certain interval before the final "Day of Judgment," where he will join Jesus in eliminating the sins of the world. The Mahdi has common associations with the Shia and Sunni sects, but they disagree with some parts concerning the return of the Mahdi. Both agree that the Mahdi will be a direct descendant of Muhammed and will bear his name. The Mahdi has been in the news recently since the Iranian government has proclaimed that recent Middle East uprisings are a sign that the Mahdi is about to appear, and one man has already declared that he is the Mahdi.
Muslims believe in Mahdi, they believe that he and Jesus will defeat Anti-Christ (Dajjal). He will come near the end of time, only Allah knows the exact timing. Jesus will return to defeat Anti-Christ. He will appear in Palestine and, after defeating Anti-Christ, will rule for forty years.
The Knowledge is with God.Only He knows when the Mahdi will come..and he will come near the end of time.. when there is so much corruptions etc