Salamun Alaikum sister,
Imam Mahdi, Dajjal, Second coming of Prophet Jesus etc are all
unquranic concepts and those that propound such concepts base their opinions on Islamic secondary sources and not the Quran.
Indeed, there is mention of a tribe of people in the past known as Yajooj and Majuj from the Quran (18:94) but this has nothing to do with Mahdi / Dajjal etc.
Most of these unquanic concepts are a direct result of the belief that Prophet Jesus will return to earth (A Christian inherited belief) for which the Quran provides no proof.
Rather, verses of the Quran seem to clearly refute such a belief.
IS THE SECOND COMING OF PROPHET JESUS (pbuh) SUPPORTED BY THE QURAN?http://quransmessage.com/articles/is%20second%20coming%20attested%20by%20the%20quran%20FM3.htmYou are absolutely correct that knowledge of the hour
is only with God which is a
fundamental belief of a true believer indoctrinated by the Quran. One begs the question as to what state one leaves their belief (vast majority of Muslims) that compromise and pollute their beliefs with alien, unquranic concepts.
Only God knows best.
Regards,
Joseph.