The Flash (Comic Book)

The Flash is a long-running comic book series published by DC Comics about a superhero who can run (and carry out other actions) at superhuman speeds. Created in 1940 by All-American Publications writer Gardner Fox and artist Harry Lampert, the Flash was successfully revived by DC in 1956 and has been in print, in some form, ever since. The 'mantle' of the Flash has been held, at various times, by Jay Garrick, Barry Allen, Wally West, and Bart Allen).

Magic Words (Volume 2, Issue 162)
Felix Faust hypnotizes a roomful of journalists at a broadcast convention, programming them to recite an incantation at precisely 6:57 PM the next day that will throw the world back into the medieval dark ages. Linda Park-West and Shazam (in his Billy Batson identity) are among the hypnotized. While at the airport the next morning, an airline employee accidentally triggers their post-hypnotic suggestion, and they recite the incantation, causing the airport to briefly devolve into a medieval state. Because it is not actually 6:57 PM, the incantation fails. It does, however allow Flash and Shazam to realize that Faust is up to no good.

They manage to track Faust down, but he confidently explains that his sleeper agents are now scattered around the globe and are all programmed to say their magic words at 6:57 Central City time, not their own local time, making it impossible to stop them all. Flash and Shazam concentrate instead on destroying Faust's transmitting equipment, foiling his plan before it can even get underway.