In the scene after "one year later" where Margaret sees Lucy again, the watch Jack gave her is missing from her wrist; however, when she walks in the room with Winston a few seconds later to look at the hourglass one more time, the watch is suddenly on her wrist.
When Lucy hits her head on the ladder the men are carrying after breaking the hourglass she hits the bottom plank of wood but in the next scene she hits the top plank of wood.
When Lucy asks the tour guide about an alternate ending he has his hands in his pockets but in the next scene he has his left hand in front of his chest.
As Jack greets Lucy when she arrives at the Christmas Eve party, he has a noticeable 5 o'clock shadow which is gone in subsequent shots.
When Lucy hands West the list of names Lancaster gave her he holds it but in the next scene it is on the counter and he has one arm folded in front of him and the other on the counter.
The actors in 1947 are staying at the Inn at Biltmore. The Inn at Biltmore wasn't opened until 2001.
The plaque next to the red dress on display reads in part, "The studio originally wanted to go with another actress, but co-star, Jack Huston knew Ms. Hayward was perfect for the role." There should not be a comma before Jack.
A fifty-star US flag flies at Biltmore in 1947. The US flag did not have 50 stars until 1960.
A number of pieces of modern film production equipment and materials are seen in 1947, or period-correct pieces are seen operating in modern ways.
When Lucy purposely travels back to 1947 dressed in period clothes from storage, she has the candy cane girl outfit over her arm, but she doesn't have the red dress she wears the next day after becoming trapped by the broken hourglass.
Lucy's surname is consistently mentioned in the movie as being Hargrove. It is listed in the end credits as being Collins.