--- Act 1 and Act 2 the characters in the play live as society does today. They all have daily routines, all have a plan for their futures, and live up to traits started a long time ago by ancestors. In society today people live and act the same way as the characters did when this play took place in the early 1900's. It's signifying time may change but people don't. Act 1 and Act 2 are used to set up and be used as examples for Wilder's main theme which is described through Act 3.
--- Act 3 was meant to be the conclusion of the play and to display and share the theme, or message, expressed in this play. The stage manager is the character who portrays and controls the time in this play. Time is important because it relates to the theme. The stage manager changes the time multiple times throughout the play. "This time nine years have gone by, friends--summer, 1913." Each part the stage manager expresses a new time, the characters act the same and the story could pick back up as if it was never interrupted. Each example of time used in this play relates to the theme, as time changes, people don't.