Jesus likens His second coming to the flashing of lightning.
For as the lightning cometh out of the east, and shineth even unto the west; so shall also the coming of the Son of man be.
No one can predict the date & time when lightning will flash. But we can recognise the conditions when lightning will flash, during a thunderstorm. Before the lightning flash, people can debate whether it will flash at any given instant. During the lightning flash, there is no doubt because everyone living in the area can see it, if they are out looking for it. After the lightning flash, people can debate whether it ever flashed at all, the only physical evidence we have that lightning actually flashed is the scorch mark it leaves behind. We have a record of the scorch mark in the case of the coming of the Son of Man: the destruction of Israel, of Jerusalem, of the Temple made of stone in 70AD.