Plot hole: After Superman has reversed time the Hoover Dam reverts to its previous undamaged state as it should, but Jimmy Olsen should then have been replaced back on the dam. Instead he interrupts the potential kiss between Lois and Superman and complains of being abandoned by Superman in the desert.
Plot hole: When young Clark Kent is being taken on a journey by his deceased father, the journey ends with Jor-El saying, "By the time we return to the confines of your galaxy, twelve of your years will have passed." If Clark was gone twelve years, how could he have managed to get a job at the Daily Planet? There would have been a background check to see which journalism school that Clark went to as well as college and also to see if he had other jobs, yet he simply gets the job without a problem. All of the people that Clark grew up with would probably be curious as to why they haven't seen or heard from him in a long time as well.