Zero Hour: Crisis in Time!

Zero Hour: Crisis in Time! was a 1994 crisis event intended to deal with numerous possible futures and alternate timelines in the same way the earlier Crisis on Infinite Earths had dealt with alternate realities. The main storyline featured the destruction of the timestream by the efforts of Parallax (Hal Jordan), attempting to restructure the universe and correct things that he perceived to be wrong. Another super-villain, Extant, took advantage of the chaos and tried to use it to re-create the world in his own image. The leader of the fight against them was Waverider of the Linear Men. The conflict resulted in an entirely new Big Bang, which rebooted the entire DC Universe with subtle differences. This served as an opportunity to clear up continuity problems, and fix plot elements and pieces of history that no longer worked well.