When will the doomsday come?

They ask you about the Hour (Day of Resurrection): "When will be its appointed time?" Say: "The knowledge thereof is with my Lord (Alone). None can reveal its time but He. Heavy is its burden through the heavens and the earth. It shall not come upon you except all of a sudden." They ask you as if you have a good knowledge of it. Say: "The knowledge thereof is with Allâh (Alone) but most of mankind know not.

Al a'raaf 187