Jack and Rebecca argue about having kids during the Super Bowl and end up conceiving their three that night. The Super Bowl was January 20, and the kids were born in late August 1980 which is only 7 months even though in the first episode they say that the triplets were 6 weeks early.
Rebecca and Jack are fighting about the idea of having kids during the 1980 Super Bowl. During their argument, a patron at the bar says, "Hey Sid and Nancy, will you two take it outside?" Though the cult classic film "Sid and Nancy" wasn't released until 1986, the volatile - if not destructive - relationship between Sid Vicious and Nancy Spungen (on whom the film is based) was well-publicized music lore by 1980, with Vicious having been arrested for her murder in 1978.
The nutrition label on the cereal that Dr. Katowski removes from the shelf did not appear until the 1990s. Cereals had nutrition and ingredient labels, but not in the style shown, in 1980.
At the opening with a flashback to Rebecca as a child. Her father is watching a football game. On screen you hear Curt Gowdy's voice talk about Joe Namath throwing a pass thru the Baltimore defense. This is the January 1969 Super Bowl 3. Rebecca appears to be about 10 years old give or take a year. Flashforward to the January1980 Super Bowl and Rebecca says to Jack she's 29, not even 30 yet. If she was at best 12 years old in the earlier scene that would make her 23 in 1980 the year Jack and her conceive and deliver the babies. The scene on the TV screen can be verified on YouTube. It is at 2:00 minute mark of the third quarter. Googling Super Bowl 3 there is a complete version of the game. The exact pass by Namath to George Sauer takes place at 2:41:35 mark of the video.