The world's greatest heroes played a major role in Zero A Crisis in Time, one of DC's most monumental crossovers ever—and now, those chapters of the Zero Hour saga are collected for the first time. All of reality comes under attack when a mysterious force of entropy begins slowly erasing time itself—making its way from both the past and future toward the present! As history itself unravels around them, the heroes of the Justice League of America across the globe scramble to fix the broken timestream. But even if they stop the true source of the chaos, the world they save will never be the same! Written by Mark Waid and others, Justice Zero Hour collects Justice League Task Force #0 and 15-16, Justice League International #67-68, Justice League America #0 and 92, The Ray #0, Extreme Justice #0 and Guy Gardner, Warrior #0 and 24.