One good example of how time is used to help create atmosphere is at the start of Act 2. Banquo and Fleance are out walking past midnight. After a brief conversation, Fleance goes in to go to bed and Banquo encounters Macbeth, also up and unable to sleep. Banquo and Macbeth speak briefly and Macbeth alludes to the witches' prophecies and to another topic he wants to talk about with Banquo. After that short conversation, Banquo retreats to the castle leaving Macbeth alone. Macbeth delivers his famous "dagger" soliloquy. That Macbeth sees this phantom dagger in front of him and then sees it again covered with blood speaks volumes about Macbeth's current state of mind because at the end of this soliloquy he goes into the castle to kill Duncan. When he does the killing, it is, of course, dark because it is night and most of the castle is asleep. Macbeth hears voices in the dark, some are real (people talking in their sleep possibly) and some are not real. None of this would be as mysterious as it is if it were daytime. The brief talk outside the castle with Banquo, the soliloguy featuring the dagger, and the killing of Duncan would have been much flatter during daylight hours. Also, midnight, or shortly after, is often associated with "the witching hour" and Macbeth's killing of Duncan has much to do with witches.