Factual error: Eddie specifically tells the gang not to take his mom's "Delicious Deals" snacks because his mom loves them. But Delicious Deals are made by Mrs. Freshley, a company that was not founded until 1994. The boxes used in the movie even include the modern design that can be found today in most Dollar Tree stores. (00:23:00)
Factual error: During the opening scene in 1988, a silver TV from the late 90's/early 00's is in the living room/dining room area. (00:02:10)
Suggested correction: There were several TVs similar to the one pictured in 1988. A quick Google search of "TV's available in 1988" will tell you this. Without knowing the manufacturer or model of the TV, you cannot state this as a movie mistake. If it was a LCD TV in 1988 then yes but, this one, no you can't assume this TV was not available.
Factual error: At the pharmacy on the shelf is Olay. It wasn't called that until 1999. It was Oil of Olay in 1989. (00:37:30)
Factual error: When Stanley is at synagogue practicing for his Bar Mitzvah, and the Rabbi tells him to close the book, he does so - and a clear shot of the book cover from Stanley's left shows that the book (in Hebrew) is upside down. Hebrew books read right to left - the cover should be on Stanley's right, right side up.
Factual error: Nivea Soft Cream is on the shelves at the chemist - this did not exist in 1989, when the film is set.
Suggested correction: I think the date is subject to debate. The only thing we really have to go on is it's 2019 in chapter 2, and It comes back every 27 years which would be 1992.
The date is not subject to debate. The marquee on the movie theater is advertising both "Batman" and "Lethal Weapon 2," placing the movie in the summer of 1989.
There is no debate about the date. After the title card it says "June 1989." The opening scene took place "October 1988."
Factual error: Police cars are shown with red and blue lights. Police cars in Maine only display blue lights.
Factual error: During the rock fight, Richie calls Henry Bowers a "mullet wearing a**hole." The term "mullet" wasn't coined until 1994 by the Beastie Boys in the song "Mullet Head." (01:07:15)
Factual error: Bill is holding a Lego turtle and drops it on the floor, then you see a closeup on the parts. Green Lego bricks were not commercially available before 1996 and lime green Lego was not available before 2003. (00:56:20)
Factual error: When Bill meets Beverly for the first time and the shot is showing her while walking towards the other guys, some modern SUV are visible in the background.
Factual error: This film is set in Maine (USA), but the war memorial shown is obviously Canadian; this is evidenced by the phrase "for King and country" engraved upon it.
Factual error: When passing under the railway bridge not only are the cars modern but there is also a Canadian Tire container on it which is a Canada only store, and doesn't ship by rail in the USA.
Factual error: In the pharmacy, there's a black bubble dome camera visible. Those kinds of camera weren't around in 1989.
Factual error: While Eddie and Bill are in the prescription section of the store, there is a security camera on the ceiling that wasn't released in the 80's.
Factual error: When a train is passing on the bridge, it has modern containers. The type of car hauling it is also one from the modern era.
Factual error: Ben's headphones look like 1995 plastic models and not 1989 style.