In classical Drama there were 3 unites, The unity of time, The unity of place and the unity of action
the unity of time demanded that the action of the play was to take place within 24 hours
the unity of place said that a single setting throughout the play should be used
the unity of action, slightly less defined, said a play should focus on the main characters without sub plots, and that action should have a satisfying ending
The 3 unities since the 15th century has been discussed by critics, aheared to and broken by dramatists, most notably by Shakespeare
Streetcar takes place only in the Kowalski's apartment, conforming to the unity of place, giving the play a tense and claustrophobic atmosphere
Streetcars spans over a couple of months and so brokes the unity of time, however scene 7-10 does happen within 24 hours