The name of the Holy Imam was the same as that of his respected great grandfather, the Messenger of Allah (a.s). The Holy Prophet saved the people from deviation and his grandson and last of the twelve successors is also the savior of humanity. Historians and tradition reporters are unanimous that his holy great grandfather, the Messenger of Allah, selected this name for him.[1]
Titles of Imam Mahdi (a.s)
The Holy Imam is endowed with numerous titles, some of which are as follows:
1. Mahdi – It is the most popular and well-known title of the Holy Imam (a.s). It is due to the fact that he would guide the people in truth and in every concealed affair. That is why he is given the title of “Mahdi”. The same title was once accorded to the Messenger of Allah, (a.s). The distinguished poet, Hisaan bin Thabit has worded the following couplet at the tragedy of passing away of the Holy Prophet (a.s):
“What has happened to my eyes that I cannot sleep
As if in my eyes is the Kohl of sleeplessness.”[2]
In the same way, the Prophet of Allah (a.s) says in his supplication,
“O Allah, embellish me with the embellishment of faith. O Allah! Make me of the guided ones.”[3]
This title was also associated with Imam Hasan (a.s). Sulaiman bin Sard, one of the prominent penitents of Kufa says, “O Allah, have mercy on Hasan, the martyr, son of the martyr, the Mahdi, son of the Mahdi.”[4]
However, this honorific is specially associated with the Awaited Imam in such a way that its application to any other personality is very rare and any reference to it is without fail associated with Imam Mahdi (a.s) as mentioned by Ibne Manzoor[5] and Zubaidi[6], the well-known lexicographers and experts of Arabic.
2. Qaim (One who rises). This is also a title of the Holy Imam Mahdi (a.s). It is due to the fact that he would arise for truth.[7] And he is also referred to as the Qaim of the Progeny of Muhammad (a.s).
3. Muntazar[8] (The Awaited one). As the believers are patiently waiting for his reappearance.
4. Hujjat[9] (Proof). This is because he is the Proof of Almighty God upon His creatures and servants.
5. Khalaf-e-Salih (the best and the righteous Successor), because he is the heir of the greatest families of the Islamic world…

Agnomen of the Imam of the time
It is a confirmed fact that the Prophet of Islam (a.s) had designated, Abu Abdillah[10] as the agnomen of his last successor, the Awaited Imam. It is also said that the agnomen of the Holy Imam is, Abu Ja’far and Abul Qasim.[11]

Year of Birth of the Imam of the Time
The birth of His Eminence, Mahdi (a.s), the great reformer of humanity is said to have been in the year 255 A.H.[12] and the year 232 all is also mentioned in this regard.[13]
The Blessed Night
The Qaim of the Progeny of Muhammad was born on the blessed night of the 15th of the month of Shaban al-Moazzam. It is the holiest night and it is mentioned in some traditions and narrations that the night of Power (Shab-e-Qadr) is this very night. And that all affairs are appointed on this night. On this night, the Ziyarat (visitation) of the father of the independent ones and the beloved of the Messenger of Allah (a.s), the chief of the Martyrs, Imam Husain (a.s) is recommended.

References
[1] Iqdud Durar
[2] Diwan, Hisaan bin Thabit, Pg. 97
[3] Musnad, Imam Ahmad, Vol. 4, Pg-264
[4] Tarikh, Tabari 7/70
[5] Tajul Uroos 1/409
[6] Lisanul Arab, 3/787
[7] Bihar 13/10
[8] Bihar
[9] Bihar
[10] Iqdud Durar fi Akhbar-e-Muntazar, Pg. 194
[11] Rauzatush Shohada, Pg. 326
[12] Wafayatul Ayan, 2/451, Usool-al-Kafi
[13] Bihar