The film is set in December 1973, but two of the obituaries Ralph looks at in the newspaper show the people died in 1974.
After Ralphie loses it about the star falling off their Christmas tree and breaking, he argues with Sandy while she is comforting Julie. Different view angle shows Sandy standing by herself, with Julie nowhere to be seen, three different times.
The eye patch Julie is wearing disappears in one scene and reappears in the next.
The December 1973 calendar shown in the opening credits is inaccurate. December 1st 1973 was a Saturday not a Thursday as shown in the movie. Consequently, Christmas day actually fell on a Tuesday not on Sunday as shown in the movie.
The story is set in Indiana in 1973. After Scut Farkus apprehends Ralph he drives Ralph home and his patrol car has blue lights. Indiana police vehicles at that time used all red lights. Blue lights were used by volunteer firefighters.
When Ralphie and his family have the snowball showdown with Black Bart, you can see the string pulling the tumbleweeds. As this is a fantasy sequence, it was intentional for the string to be shown.
The first page of Ralphie's manuscript has a typo: "annial" instead of "annual" (second paragraph)
When Ralphie gets the newspaper out of the mailbox and sees his story, there is a moment when the paper blows toward him and you can see that the back of the page (which should be page 2 of the newspaper) is blank.
Ralphie's daughter says she wants the Hungry Hungry Hippos game for Christmas. The movie is set in 1973 and the game wasn't introduced by Hasbro until 1978.
The Palmolive Building is visible in the shot of the Chicago skyline from the north. However, it is missing the Playboy logo that was near the top of the building for decades until the late 1980s.
Early in the film, Ralph uses the CTA to take the train in Chicago. The sign says 'Redline'. However, the Chicago Transit Authority train system used street names for different train stops until February 21, 1993, when they unveiled new designations that used color-coded train signs and maps for the various routes across the city.
The cash register seen in the department store when Ralphie is shopping is not accurate to 1973.
Several cars are not accurate to 1973, such as a parked Chrysler Cordoba introduced in 1975.