now that you have understood these meanings it should be said that such sayings as: Mahdi will emerge in «--» (end of time) or that: he is the caliph of «--» refers to the last meaning which means that the last part of the period in which Mahdi is supposed to emerge is the last part from the parts of time.
the author of 'eqdud-durar' (in chapter seven) narrates from hafez abu abdullah (from the book of mustadrak) who narrates from abu sa'eed khudri that the messenger of Allah (s.a.w.a.) said:
'Mahdi shall emerge with the sword at the time of the end of my nation. Allah shall send rain, the land will cause its own plants to grow, (Mahdi) will bestow wealth in the right manner....
hakim says: this tradition is correct as far as its chain of transmission is concerned but muslim and bukhari have not narrated it.
again, the author of 'eqdud-durar' in the afore-said chapter narrates from hafiz na'eem-ibn- hemad (from the book 'fatan') that amir-ul- mumineen ali (a.s.) said in one tradition about Mahdi as such: 'Mahdi will rise when he would be thirty or forty years of age....
in the same chapter of the afore-said book its author narrates from abu abdullah mada'eni and abu bakr baihaqi that ibn-abbass said: i have hope that days and nights will not pass until Allah will appoint a youth from us, ahl-e-bayt while conspiracies will not befall him and he too will not be entangled in conspiracies. he will establish the affairs of this nation just as Allah commenced the affairs of this nation through us. it is my expectation that the affairs would end too in us.
narrator says: i told ibn-abbass: are your aged helpless in this matter that you have hope in your youths? he replied: Allah does whatever he wishes.
in the same chapter of the same book, its author narrates from imam hussein-ibn-ali (a.s.) as such: when Mahdi will emerge, the people will deny him because he will have returned to them looking like a youth. the greatest calamity is that their master will approach them in the state of youth while they would think him to be old and senile....