Say:"(Yes) verily, those of old, and those of later times. All will surely be gathered together for appointed meeting of a known Day."meaning, `Say, O Muhammad, that the earlier and latter generations of the Children of Adam will be gathered for the Day of Resurrection and none of them will be left out.Allah the Exalted said:ذلِكَ يَوْمٌ مَّجْمُوعٌ لَّهُ النَّاسُ وَذَلِكَ يَوْمٌ مَّشْهُودٌوَمَا نُوَخِّرُهُ إِلاَّ لاًّجَلٍ مَّعْدُودٍيَوْمَ يَأْتِ لَا تَكَلَّمُ نَفْسٌ إِلاَّ بِإِذْنِهِ فَمِنْهُمْ شَقِىٌّ وَسَعِيدٌThat is a Day whereon mankind will be gathered together, and that is a Day when all will be present. And We delay it only for a term fixed. On the Day when it comes, no person shall speak except by His leave. Some among them will be wretched and (others) blessed. (11:103-105)He also said here,لَمَجْمُوعُونَ إِلَى مِيقَاتِ يَوْمٍ مَّعْلُومAll will surely be gathered together for appointed meeting of a known Day.because that time is precisely designated and will not come late, early, nor increase or decrease.Allah said,ثُمَّ إِنَّكُمْ أَيُّهَا الضَّالُّونَ الْمُكَذِّبُونَ