In the hockey-game scene, the Philadelphia Flyers are wearing orange sweaters, while the visiting Edmonton Oilers are wearing white sweaters. In the NHL in the 1980s, the home team always wore white, so the Flyers should be wearing white while the Oilers should be wearing blue.
Murray complains that his father took him to see Psycho when he was 9 years old. Psycho (1960) was released in 1960, meaning Murray would have been born in 1951. This is utterly impossible as it would make him 29-38 years old in the show, even though he and Bev have been married for 25 years and have three teen children. Later in Season 4 we see Murray's 50th birthday party, meaning he was actually born sometime in the 1930s.
As always, this starts with Adam identifying it as occurring in "1980-something" as well as a later voice-over of events "started the answering machine war of 1980-something", both saying this is in the 80s. However, when Adam finds the computer room, he says "Whoa, is that Prince Of Persia?". Prince Of Persia was released in 1990. Adam's familiarity with it makes it likely 1991 or 1992, but it's still the 80s.
One of the fans at the Flyers game was wearing a black Flyers jersey. The black third jersey was introduced during the 1997-98 season.