Continuity mistake: Sam's shoes are light colored high heels while she is sitting on the stairs with John talking to Ted before he got mad and left, eventually ending up in Comic Con. They're black flats when she and John are looking for Ted all the way through to when John was hit by the Enterprise.
Factual error: Ted is driving the car and goes airborne into a barn where the car comes to a sudden stop. Samantha, who is sleeping in the back seat without her seatbelt, doesn't shoot forwards from the rapid deceleration.
Answer: Films are basically never set exactly when they're released. Most likely they just picked a random date around the likely time of release, but scheduling changed. Alternatively they just picked an arbitrary date in the future for the newspaper, but a date in the recent past would have worked just as well.