﴿ ذَٰلِكَ ٱلْيَوْمُ ٱلْحَقُّ ۖ فَمَن شَآءَ ٱتَّخَذَ إِلَىٰ رَبِّهِۦ مَـَٔابًا ﴾

“That will be the Day of Ultimate Truth: whoever wills, then, let him take the path that leads towards his Sustainer!”

That is the True Day whose coming to pass is definite namely the Day of Resurrection. So whoever wishes to let him seek resort with his Lord a return to Him that is to say let him return to God by being obedient to Him so that he may be secure from chastisement in it.