Deliberate mistake: Though the film takes place over the course of several weeks, at night there is always a full moon.

Watchmen (2009)
1 deliberate mistake - chronological order
Directed by: Zack Snyder
Starring: Patrick Wilson, Carla Gugino, Matthew Goode, Billy Crudup, Jeffrey Dean Morgan, Jackie Earle Haley, Malin Akerman

Revealing mistake: During the final confrontation in Veidt's lair, you see the actor Billy Crudup in his SFX suit reflected in Nite Owl's goggles, not the image of Dr. Manhattan.
More trivia for Watchmen
Question: How come the surviving members of the Watchmen (with the exception of Rorshach) agreed to let Dr. Manhattan take the blame for the murders of so many people? Wouldn't it have been easier to just arrest Veidt and let everyone know who was truly responsible for everything?





Answer: The entire reason they don't arrest Veidt is because his actions, while evil and genocidal, did in fact cause the two warring nations to unite. Exposing Veidt would revert the world back to its chaotic state and the peace would end. The millions Veidt killed would've died in vain and the Watchmen can't have that. All of this is discussed in great detail.
Brad ★