On which day do Mercutio and Tybalt die in the play Romeo and Juliet?
The action happens very quickly in this play. Mercutio and Tybalt die on a Monday. We know this because the play opens on a Sunday at 9 a.m. We can establish this fact because the evening of the next day, in Act III, scene iv, Paris will mention it is Monday.
This is the sequence of events: Sunday night, Romeo and friends attend the Capulet party. This is sometime near mid July, for Lady Capulet notes it is only a fortnight (two weeks) and a few days until Juliet's 14th birthday on August 1. At the party, Romeo and Juliet meet and fall in love. Later that night, during the balcony scene, the two decide to get married. The next day, a Monday, Friar Laurence secretly marries them. Shortly after that, Tybalt kills Mercutio, and Romeo, despite his understandable desire to avoid a fight, kills Tybalt out of grief and anger over Mercutio's death. Romeo is then banished and Juliet's parents, not knowing about the marriage, decide she will marry Paris on Thursday.
We know that these deaths, which occur in Act III, Scene 1 of "Romeo and Juliet," occur on a Monday.
We know this because it occurs on the day after Romeo and Juliet have secretly been married. This marriage actually helps to cause the deaths. Romeo does not want to argue with Tybalt at first because he feels like they are now kinsmen. But then Tybalt kills Mercutio while Romeo is trying to break up the fight.
So in this way, the day on which the killings happen is related to the plot.