Time Shards - Tempus Fury — Dana Fredsti

Time shatters into shards of the past, present, and future. A group of survivors dodges threats from across history to locate the source and repair the damage before it's too late.
 

When time shatters, the survivors must fight their way to the ends of the Earth before it's too late.
 
They call it “the Event” -- an unimaginable cataclysm that renders 600 million years of the world's timeline into jumbled fragments. Our Earth is gone, instantly replaced by a new one made of fractured remnants of the past, present, and future. All exist alongside one another in a nightmare patchwork of “time shards” -- some hundreds of miles long, and others no more than a few feet across.
 
With surprising help from throughout history, an American girl and her companions first must save ancient Alexandria, the last bastion of civilization, from a panzer tank invasion. Then they will face the ultimate challenge at the end of the world… the shatterfield.
 
Crossing it sends them on a final quest spanning time, space, and dimensions. Only then will they learn if their mission will save their world -- or destroy it.