Factual error: In scenes that take place in 1912 on the porch of the hotel you can sometimes see American flags in the background. The flags in the movie have 50 stars. The 50 star flag wasn't adopted until after 1959. (01:25:15)
Factual error: In 1912, Richard Collier gives young Arthur his ball, and above their heads, you can see the 1980 fire sprinklers in the ceiling. (00:40:40)
Factual error: When Richard Collier encounters the young Arthur in 1912, Arthur is playing with an inflatable rubber ball. Balls of this style were not made until the 1960s.
Factual error: The 1912 hotel has frosted light bulbs hanging from the ceiling in some scenes. Frosted bulbs weren't around until the 1940s. (00:43:15)
Factual error: When Richard and Elise are walking down a hallway, he asks when the acting company will leave. Notice the two doors they pass on their left. The doorknobs are modern replacements with large, shiny brass plates that reinforce the door for better security, commonly retrofitted during 1960-1980 in public buildings with older "skeleton key locks". They are seen during the 1980 scenes, but in 1912 they should not be there. Interior locks of that era usually had smaller plates, like the one Richard first sees in the occupied guest room.
Factual error: When Richard Collier first arrives in 1912, the woman getting dressed in the hotel room is humming "You Made Me Love You," a song not published until 1913. It was first recorded by Al Jolson in June of 1913. The lady in the hotel shouldn't have known it yet. (00:30:00)
Factual error: When Richard first enters the 1912 theatre looking for Elise, he passes through a propped-open door that's equipped with a modern day hydraulic closer. (00:42:00)
Factual error: In the final sequence, Richard Collier is shown sitting in a chair where, as others break into his room, we are lead to believe "he had been for days". Yet his hair is clean and combed, his clothing seems immaculate, and apart from some makeup, he shows no sign of any mental or physical problems.
Factual error: When Richard Collier follows Elise into the restaurant all the men are wearing hats. Their hats would have been checked at the door.
Answer: There are several things like this throughout the movie. It's a rather busy location.