Lightness and darkness are used as symbols throughout Shakespeare's plays. The fact that the conspirators are meeting at three in the morning reflects their evil intentions. The disagreement occurs in Act II, Scene i of the play. The conspirators have just arrived at the home of Brutus to finalize their plot to kill Caesar. Brutus shakes hands with everyone, and then he and Cassius talk, away from the others, furthering the idea of the cloak-and-dagger atmosphere of the conspirators. The disagreement of where the sun rises is between Decius, Casca, and Cinna. This part allows Cassius and Brutus to talk privately,  but more importantly, it foreshadows the murder of Caesar. Casca points out that due east is not only the direction of sunrise, but it is also the direction of the Capitol where Caesar will be killed. This provides the irony of this scene. Sunrise is a symbol of life and awakening, and sunset represents death and darkness. The irony then is that the death of Caesar will occur in broad daylight.