Continuity mistake: As Maya is showing Tony her research, in the shot where Tony says "Essentially, you're hacking into that of the genetic operating system...", Tony is shown to be looking at Maya. Then as he finishes off the sentence with "of a living organism" in the following shot, Tony is suddenly looking at the computer. (00:02:55)
Continuity mistake: When the suit starts to arrive at the bad guy's house in bits, Tony Stark is walking down a long hallway. Scene cuts to outside and his facemask arrives, but the building he is in front of isn't big enough for the hallway we just saw. (01:28:15)
Continuity mistake: After Tony hangs up on Happy using Face-Time, the scene cuts to Pepper and Killian having a conversation. As Pepper says "As in, enhanced soldiers, private armies, and Tony is...", she is cut off by Killian. When Killian starts speaking, he shifts his head to the left and starts looking downwards. In the next shot, he is suddenly looking straight back up at Pepper. (00:17:45)
Continuity mistake: When Tony tells Killian to go to the roof, he leaves the lift. In this shot, there is a strand of Killian's hair layed over his face and nose in a straight line. In the next shot as he says "I'll see you up there", the bottom of the strand is suddenly curved over to the left side of his face. (00:02:40)
Continuity mistake: In 1999, when everyone exits the lift, Tony and Killian stay inside the lift. As everyone leaves, Tony places his hand on the door frame. In the following close-ups of Tony and Killian, Tony's arm never shows any signs of moving his hand, but as he leaves the lift, his hand is no longer on the door frame. (00:02:35)
Answer: With the release of Endgame, it is now fact that the Battle of New York took place in 2012.