When Benetha is talking to mama and getting ready to go out with George, the bracelet on her left arm keeps disappearing and reappearing.
A newspaper Beneatha reads in the first scene includes a headline about an event that happened in July 1960, but Travis has just left for school. Public schools would have been in summer recess in July. Also, it isn't dark in Chicago at 5 o'clock in July. That would only happen October to January, and nobody is seen wearing cold weather jackets, etc.. Also, the calendar in the kitchen does have 31 days, but starts on a Wednesday. July 1960 started on a Friday.