Howard and Paul live next door to Lisa in an apartment building. In the opening scenes, Lisa and Paul each come out of their respective apartments into the hallway at the same time, establishing her apartment on the left and the boys' apartment on the right. Later in the movie, after Paul and Howard have gone out to dinner, the same apartments are filmed from the opposite side (through the outside windows), but instead of being mirrored as they should be (with the boys' apartment on the left and Lisa's on the right), Lisa's is still on the left and Howard and Paul's are still on the right.
Willy comes out with a bottle of wine and holds it at the neck, pouring. When the camera changes for a closeup of the pouring he then holds it by the base of the bottle.
In the first scene, which takes place on July 3rd, 1981, people are shown working in an office. In 1981, July 3rd was a Friday, which would have been a holiday for most businesses since July 4th was a Saturday.
In the second act, dated April 1982, Howard and Paul are discussing how Howard will play one of the first gay characters in a daytime soap opera. Howard says it's fine for an actor like William Hurt to play a gay character but not him. He is obviously referring to Hurt's role in Kiss of the Spider Woman (1985), for which Hurt won an Academy Award for Best Actor. But that film came out in 1985, three years after the time in which this scene is set.
In the segment marked "July 3, 1981" people dance to the song "Do You Wanna Funk?" by Sylvester, but this song was not released until 1982.
In the opening act set in July 1981, a character plays a tape of The Human League's song "The Things That Dreams Are Made Of". However, this song was not released until October 1981 when it appeared on the band's album "Dare".