Nancy Kress

Harry bought a pair of socks, thick gray wool, for 89 cents. When the man took his dollar, Harry held his breath: each first time made a little pip in his stomach. But on one ever looked at the dates of old bills. He bought two oranges for five cents each, and then, thinking of Manny, bought a third. At a candystore he bought G-8 and His Battle Aces for fifteen cents. At The Collector’s Cozy in the other time they would gladly give him thirty dollars for it. Finally, he bought a cherry Coke for a nickel and headed towards the park.

They’re often like this. They find themsleves in an alien, impossible, unimaginable place, surround by guards with uniforms and weapons they don’t recognize, and yet their first concern is not their personal fate but the battle they left behind.

No. No travel is involved. A user cannot affect anything that has happened, ever. All the Chrono does is show on a screen what is already there, was there, will always be there.