Seven days until the end of the world

The world is doomed. The exact date of the apocalypse is known. In order to save everyone, scientists create a Machine on a remote island that starts a time loop. Now humanity is forced to live the same hot summer week over and over again. The world is engulfed in chaos, because you can do anything with impunity, even rob or kill, and from next Monday the cycle will begin again, only memory will remain.
But slowly the madness subsides, and humanity begins to get used to it and build a new order. But what if the Machine does not work as reliably as it seemed? Can the former scientist whose research launched all this, and a desperate military man find a way to return the future? And does it really still exist?