All of 10,000 BC

Off the top of my head:

• Horses weren't domesticated yet

• Mammoths were already extinct (at least in Egypt)

• No one was building pyramids

Also I don't know if this counts but it really bothers me when a movie is set in a very particular place but shot in a completely different biome. The most egregious examples I can think of are:

• Diamonds Are Forever, which was filmed entirely in Nevada, but is partially set in South Africa. Like dude I can tell that's the same desert you filmed like 10 minutes ago, don't try and tell me it's the Kalahari or whatever.

• Alien vs. Predator 2: Requiem: besides being a terrible film that shits all over the Alien and Predator franchises, it expects us to believe that a temperate rain forest in British Columbia full of ferns and shit is fucking Colorado.