Almighty Allah says in the Quran:

'And they say, “When will this promise be fulfilled, if you are truthful?” Say, “Knowledge is with Allah, and I am only a clear warner.”' (Surah al-Mulk verses 25-26)

The Prophet peace and blessings of Allah be upon him, among other teachings of Islam, said that eventually the doomsday would be reckoned and every person would be punished and rewarded for what he did in this world. The polytheists of Mecca asked, "When will the Day of Judgment you promise come?" The question arose from a lack of confidence. The Holy Quran emphasizes that only Allah knows when the Day of Judgment will come, but the Prophet peace be upon him is only a warner.

On the other hand, those who are unaware of Islamic teachings are spreading rumors about the Doomsday, causing confusion among the people.

The next verse mentions certain events that will occur on the Day of Judgment.

'But when they see it approaching, the faces of those who disbelieved will turn gloomy, and it will be said, “This is what you used to call for.” Say, “Have you considered? Should Allah make me perish, and those with me; or else He bestows His mercy on us; who will protect the disbelievers from an agonizing torment?” Say, “He is the Compassionate. We have faith in Him, and in Him we trust. Soon you will know who is in evident error.” Say, “Have you considered? If your water drains away, who will bring you pure running water?”' (Surah al-Mulk verses 27-30)

Narrated AbuHurayrah:

The Prophet peace be upon him said: A surah of the Quran containing thirty verses will intercede its reader till he will be forgiven. That is: "Blessed is He in whose hand is the sovereignty" (Surah al-Mulk).