Time's Holiday — Jennette Marie Powell

In this short story, seventeen-year-old Taylor Gressman sneaks away on Christmas Eve, hoping to find the angel who recently saved her life. Instead, an unexpected trip back in time plunges her into the midst of a murderous street gang. Now Taylor must ensure that she and a newfound friend don't become the gang's next victims, and in the process, learn that giving is the best gift of all.

“Time's Holiday” is a prequel to the Saturn Society novels, and takes place a few years before Time's Enemy, Saturn Society Book One.