Time and Venue of the reappearance of His Eminence, the Master of the Age (a.s)
Here we shall discuss in brief traditions of the Messenger of Allah (a.s) regarding the time and place of reappearance of His Eminence, system of his government and the special characteristics of the companions of His Eminence.
Time of Reappearance
As for the time of the reappearance of His Eminence, Imam Mahdi (a.s), it would be a Saturday of the month of Mohurrum. It shall be the day when the chief of the martyrs, Imam Husain (a.s) was martyred (10th Mohurrum).
1. Abu Basir narrated from Imam Ja'far Sadiq (a.s) that he said, “Our Qaim shall reappear on Saturday, the day of Ashura – the day when Imam Husain (a.s) was martyred.”
2. Ali Ibne Mahziyar narrated from His Eminence, Imam Muhammad Baqir (a.s) that he said, “As if I am seeing the Qaim on a Saturday, the day of Ashura, standing between Rukn and Maqam and Jibraeel is in the front calling that oath of fealty be given to him for the sake of God. Then he shall fill the earth with justice and equity like it would have been full of injustice and oppression.”
 Kamaluddin  Ghaybah, Shaykh Tusi
3. Abu Basir narrated from Imam Ja'far Sadiq (a.s) that he said, “Our Qaim shall not reappear but in an odd numbered year, like one, three, five, seven or nine, on the day of Ashura and (it would be) a Saturday. He shall stand between Rukn and Maqam and someone standing before him would be calling: ‘Allegiance, allegiance!’ Thus the helpers of His Eminence shall rush towards him from all around the world and give allegiance to him. Then through him the Almighty Allah would fill the earth with justice and equity, just as it would have been filled with injustice and oppression. Then he would move from Mecca to Kufa and camp at Najaf. From there he would dispatch his armies to various cities.”
Time of the call of the Angel
As for the time of the call of the angel or Jibraeel and his glad-tidings about the reappearance of His Eminence, Imam Mahdi (a.s) it is the eve of 23rd of the month of Ramadan. Some of the traditions about this are as follows:
Muhammad bin Muslim says: A person asked His Eminence, Imam Ja'far Sadiq (a.s), “When would your Qaim reappeara” He replied, “When misguidance shall be more and guidance less… at such time, with the blessed name of Qaim on the eve of the 23rd of the month of Ramadan a call shall be issued and he would arise on the day of Ashura.”
And it is said that the call of the angel is in the month of Ramadan and the reappearance of His Eminence is in the month of Shawwal of an odd numbered year.
 Muntakhab al-Athar, Pg. 465, quoted from Kashful Astar, Pg. 181  Kashful Astar, Pg. 181  Yanabiul Mawaddah, Pg. 194
Widespread Power of the Imam of the Time (a.s)
His Eminence, the Awaited Imam (a.s) is the first ruler of Islam whose dominion shall stretch from the east to the west and in the world there would be no command without his command.
1. Ibne Abbas has narrated from the Messenger of Allah (a.s) that he said, “Caliphs, successors and proofs of God on the creatures, after me are twelve persons. The first of them is my brother and the last of them is my (great grand) son.” It was asked, “O Messenger of Allah (a.s)! Who is your brothera” He replied, “Ali bin Abi Talib (a.s).” He was asked, “Who is your sona” He replied, “Mahdi, who would fill the earth with justice and equity just as it would have been fraught with injustice and oppression. By the One Who has sent me as a giver of glad tidings, even if a solitary day remains for the tenure of the world, the Almighty Allah shall prolong this day till my son, Mahdi reappears in it, then His Eminence, the Spirit of Allah, Jesus son of Maryam shall descend (from the heavens) and stand to pray behind the Imam and the earth shall be washed in divine light and his rule shall surround the east and the west.”
2. Abu Saeed Khudri narrated from the Messenger of Allah (a.s) that he said, “The world shall not end till a man from my Ahle Bayt (a.s) is at the helm of affairs and fills the earth with justice and equity just as it would have been fraught with injustice and oppression…”
3. Abdullah Ibne Abbas narrated from the Messenger of Allah (a.s) that he said, “Four persons had been absolute rulers on the earth, two were believers and two infidels. Thus the two believing ones were Dhulqarnain and Sulaiman Hashmatullah and the two infidels were Bakht-e-Nasr and Nimrod and soon the fifth one, a person from my Ahle Bayt (a.s) shall be its undisputed ruler.”
 Faraidus Simtain, Yanabiul Mawaddah, Pg. 447  Al-Arful Wardi, Pg. 2/63