This Quranic text affirms events of the real life. Each nation has a time in which it will end, so does every human being. Both nations and humans have their specified terms.

( وَلِكُلِّ أُمَّةٍ أَجَلٌ ) (And for every nation is a [specified] term): Which means a certain moment or point in time.

( فَإِذَا جَاءَ أَجَلُهُمْ لَا يَسْتَأْخِرُونَ سَاعَةً ) (So when their time has come, they will not remain behind an hour): (hour) is a contemporary word we use to indicate a duration of 60 minutes. But in this verse, the word (hour) refers to a set time. Thus, the time when the end comes is set precisely. Allah (swt) clarifies this matter by saying:

 وَمَا كَانَ لِنَفْسٍ أَن تَمُوتَ إِلَّا بِإِذْنِ اللَّهِ كِتَابًا مُّؤَجَّلًا

(And it is not [possible] for one to die except by permission of Allah at a decree determined.) (Al-i-Imraan: 145)

The reality proves this Divine Law. No one can escape this destiny, and no nation could deviate from it; neither the Caesars, nor Khosrow’s, nor the Romans or Persians. All these previous nations and cultures have ended when their time had come. Then: (they will not remain behind an hour, nor will they precede [it]). When a person dies, then Doomsday begins for him because he therewith enters the second stage. There is a life, which is the worldly life, and another one which is the life after death  and before the Day of Resurrection (Al-Barzakh).