Factual error: The basketball court in the gym has a 3-point arc. High school didn't adopt the three-pointer until 1987-88. (01:00:00)
Factual error: When driving on the roads on the way to Boston, Mr. Hunham's car passes by a red house where you can see what is a parked 2000's car, though obscured only slightly by some branches from a bush or tree. (01:23:30)
Factual error: In a shot where Mr. Hunham's car is driving towards the camera past a brown building, there are a few modern 2000s cars parked in the open that are very easily noticeable since the shot zooms in on the car as it passes by them. (01:23:58)
Factual error: The helicopter shown in the film (N801JB) was manufactured in 1979, 8-9 years after the film was set.
Factual error: When Angus and Mr. Hunham go to the liquor store, the sign on the door shows that they are open on Sundays. In 1970, Massachusetts still had blue laws in effect, and a liquor store would not have been open on a Sunday.
Factual error: During the Christmas party, "Silent Night" by The Temptations' Silent Night is playing. That version of the song, with Glenn Leonard singing lead, wasn't released until 1980.
Answer: Maybe since they didn't know how to get there, it would be easier than finding a map and trying to navigate there on their own in the snow? Just a guess, though.