Wilson, Nathan D. Outlaws of time.

"Sam Miracle never thought that his future could lie in the past. But after leaping through centuries at the side of a mystical time walker, Sam and his best friend, Glory, know that the next morning's sun could belong to yesterday as easily as tomorrow. But no day is safe. Since the Vulture escaped, Sam and Glory's greatest nemesis has left no time nor place unmarked by his path of destruction. At least Sam and Glory have Peter, the youngest version of their mentor, Father Tiempo, to help repair the sands of time... until they don't. Determined to save their friend from the Vulture's clutches, Sam and Glory put their trust in Ghost, a creature from before time itself. But now, the sidekick must fill the legend's shoes, the hero must play backup, and the powers they have yet to discover might just hold the key to protecting every last second for eons to come." --

Ages 8-12