The Madhi of course is the Christian Two Witnesses. Islam believes there is one person, but in reality there are two who will appear at the end giving testimony to the world (Rev 11; Zech 4:3). They are the two olive trees or lamps in the presence of God.
The Islamic website, Endtimes2014 writes:
Most likely, the beginning of the End of Time, including the emergence of the Imam Mahdi (Mehdi), is in 2014, and Jesus Christ (p)'s return [or second (2nd ) coming] in 2022, in-sha-Allah (if God is willing).
Our latest research seems to indicate that, most probably, the first phase of the End of Time will start when the first evil person (أعرج Araj, False Elijah / Elias, Messiah son of Joseph, etc.) arrives. This will trigger the Imam Mahdi (Mehdi) (ظهور أو خروج الإمام المهدي) to appear, in-sha-Allah (if God is willing).
The last evil person (Dajjal / Anti-Christ المسيخ / المسيح الدجال , False Messiah son David, etc.) will come (or return) in year 2022 . In response, Prophet Jesus Christ son of Mary (p) (نزول النبي المسيح عيسى إبن مريم) will come down from Heaven to Earth and end Kingdom of the Dajjal (AntiChrist), in-sha-Allah (if God is willing). Thus, the first phase of the End Times will end in 2022 (1444 Hijri ).
The Jews are expecting two Messiahs to arise in the End of Days (End of Time): the first one is Messiah son of Joseph and the second one is Messiah son of David. The Christians are expecting two witnesses to come before Jesus Christ. The Christians believe one of the witnesses is going to be Prophet Elijah (Elias). The first evil person (Araj or Dajjal) who will probably come in 2014 may falsely claim to be Messiah son of Joseph and one of the witnesses expected by Christians. The last evil person (Dajjal or Anti-Christ) who will appear (or return) in 2022 is likely to falsely claim to be Messiah son of David of the Jews and Jesus Christ of the Christians.
The following numerical analysis indicates that Barack Obama is likely to be the first Dajjal...