A secret project in the U.S. Department of Energy developed "hot fusion." It started out as hot fusion. When the hot fusion accelerator was ignited, it worked, with one anomaly - it unleashed a "time storm." The storm was unexpected. It's a tear in time that causes the grand unified field that binds the superstring structure of the universe together to warp and fold time itself. They created a "time tunnel." When they turned the engine on, when the storm erupted, it took them four hours to lock down one end. In those four hours, there were changes in the world above. Changes in history.
Because of the involvement of the universal field, the time storm not only involves a warping of the space-time continuum but also a fundamental alteration of reality itself on a universal scope. This altering of reality means the laws of physics and causality simply don't apply in the time folding process. Therefore, history can be changed and even paradoxes can occur.
The project staff labeled those 240 minutes in which history was first changed "The 240." Down in the core, they were protected. They are the only ones who remember how the world used to be before The 240.
The rings in the tunnel form a lightning rod of sorts to draw the storm in when they need to. Although they locked down one end of the time storm, the other end is out of control. Whipping around in the past. When it changes events back there, it ripples forward and changes things in the present. They have a computer that shows ripples that represent what the time storm is doing in the past. If the ripples move an unseamly amount they send a team back to attempt damage control. They can only go where the storm takes them.