Explaining the Day of Decision and what occurs during it

Allah says about the Day of Decision -- and it is the Day of Judgement -- that it is at a fixed time, with a set appointment. Its time cannot be added to or decreased. No one knows its exact time except Allah. This is as Allah says,

وَمَا نُؤَخِّرُهُ إِلاَّ لاًّجَلٍ مَّعْدُودٍ

إِنَّ يَوْمَ الْفَصْلِ كَانَ مِيقَاتًا (Surely the Day of Decision is an appointed time...78:17). 'The Day of Decision' refers to the Day of Resurrection. It is a fixed appointment. Other verses indicate that the trumpet will be blown twice. When it is blown the first time, the entire world will come to an end. When it is blown the second time, people of the entire world, the earlier generations as well as the latter generations, will be resurrected and come in multitudes and droves. Sayyidna Abu Dharr Ghifari رضی اللہ تعالیٰ عنہ reports that the Holy Prophet ﷺ said: "On the Day of Resurrection, people will come in three different groups: [ 1] a group will come in the Plain of Gathering whose stomach will be full, wearing clothes and riding mounts; another group will come to the Plain of Gathering bare feet; and a third group will be brought on the Plain of Gathering being dragged on their faces." [ Mazhari cites the following authorities: Nasa'i, Hakim and Baihaqi ]

Some narratives report ten types of group. Some scholars say that the groups on the Plain of Gathering will be divided according to their deeds and character. The narratives are not conflicting. All of them may be true.