Continuity mistake: After Sam and Tara escape the corner store, as the scene is about to end, you can see a police officer behind Sam. It then cuts to a final wide shot and suddenly the officer has moved about 10' to her right between cuts.
Audio problem: When Sam is talking to Ghostface for the first time, as Ghostface says the words "I'm going to show the world who you really are," the camera cuts to a different angle. If you watch Sam's chin at the top of the screen, you can blatantly tell that she's speaking, but no audio is heard.
Continuity mistake: When Detective Bailey picks up Sam's ID at the crime scene, pay attention. When it cuts from the close-up to the wide shot, the Ghostface mask on the floor rotates 90 degrees counter-clockwise. It's hard to see because it's in the distance, but once you see it, you can't miss it. (Use the evidence marker labeled "8" as a reference point.)
Continuity mistake: When Sam and Danny are talking and Danny jokes about having a kink for women who are ashamed to be seen with him, he goes from having his head tilted to the left to suddenly being tilted to the right between cuts.
Continuity mistake: When the girl throws soda at Sam's chest and calls her a "murderer," watch closely. As Tara and Chad hold Sam back, they swap which side of Sam they're on multiple times depending on the camera angle. The way Anika is holding back Mindy also changes between angles at the same time.
Continuity mistake: When Sam and Tara are arguing after they leave the party, watch closely. The back of Tara's bandana moves on and off her shoulder repeatedly as it cuts back and forth.
Continuity mistake: When Chad is trying to psyche Ethan up to go talk to the girl at the party, when Chad says "You got the confidence!", pay attention. Chad's hands go from down by Ethan's waist to up right next to his shoulders between cuts.
Continuity mistake: When Chad and Ethan take the shots at the party, in between shots, the shot glass goes from being below the camera to being upright at his mouth between cuts.
Continuity mistake: When Mindy and Anika are at the party, and Anika says, "Being at a house party after you were almost brutally murdered at a house party," pay attention. Anika pretty blatantly goes from facing away from Mindy to facing Mindy between cuts.
Audio problem: When Sam leaves her apartment to go find Tara at the party, we hear her in the background unlock a single lock and open the door. However, earlier, we saw that there are four different locks on the door, and she relocked all of them. So we should have heard her unlock four locks before being able to leave.
Continuity mistake: When Sam is at her apartment at the beginning of the film and is talking to Quinn before going to find Tara at the party, pay attention to Sam's hair. There are multiple times with the amount of hair that is in front of or behind her shoulders changes as it cuts back and forth between her and Quinn throughout the scene.
Continuity mistake: When Sam returns to her apartment at the beginning of the film, she is carrying two envelopes. When she hears the noise and turns around scared, she goes from holding the envelopes in just her left hand, down by her waist, to suddenly holding them with both hands up by her chest between cuts.
Audio problem: When Sam returns to her apartment, we see that she's installed four separate locks on her door due to her fear. However, when she enters and relocks all the locks, you hear her re-locking six locks.
Audio problem: When Jason dies, he says the line, "But we have to finish the movie." If you pay attention, his mouth isn't moving for the word "but."
Continuity mistake: When Jason collapses after being stabbed, the pictures on the refrigerator behind him change slightly between edits, as it cuts to a wideshot. It happens quickly, so you have to pay close attention. (Like some of them shifted during the different takes as he slid down.)
Revealing mistake: When Jason is getting stabbed to death, there's a quick 2-second shot showing him being stabbed repeatedly in the stomach, with part of his intestines hanging out. But if you pay close attention, there's no actual damage occurring with any of the stabs, revealing it's just an effect. Likely either a collapsible prop knife or a CGI knife being stabbed into him.
Continuity mistake: After Jason washes his hands, his phone rings. In the wide shot, his phone is about 3" from the edge of the counter. In the closeup, the phone is actually hanging about 1" over the counter.
Continuity mistake: When Jason is looking at Professor Crane's dead body, the amount and pattern of the blood on the front of her dress, and the position of her head changes slightly between the two shots we see her. There is significantly more blood in the second shot, and her head is tilted down a bit more.
Continuity mistake: When Professor Crane is killed, the amount and pattern of the blood dripping from her mouth and down her chin changes subtly between shots, at one point.
Continuity mistake: When Professor Crane is in the alley and the Ghostface voice says "No, it's not," she's scared by four people in Halloween costumes behind her. The way they're standing and walking by changes between shots.
Answer: I think this is more "trivia" than mistake. There's no error in a film taking place a bit further ahead in time than in its release date.
TonyPH