The Koran tells about the time of Resurrection

Disbelievers always asked the Prophet to tell them about the exact time of Resurrection:

They will way their heads at you and say: “when will it be?” say:
“Perhaps it is near!” (17/51)

Then they will ask the prophet again:

They will say: “when will this promise (Divine Promise) be, if you have been so truthful”? (10/48)

The Koran says to the prophet to tell the disbelievers that he is
( the Prophet) is only a messenger, he definitely knows there will be Resurrection but only God is aware of the time:

If I only knew whether what you are promised is near or far as away! (21/109)

Yet when they see it close at hand the faces of those who disbelievers will look wretched and someone will say: “this is what you were appealing for”! (67/27)

Resurrection will start with death; the purgatory is the beginning of the Resurrection.