In Act I of Romeo and Juliet, we come to know that the Capulet family are hosting a party (or feast) that night. Lady Capulet hopes that Juliet will take a liking to Paris at this party and agree to marry him. Of course, Juliet has her fateful meeting with Romeo at this party and pays no mind to Paris at all.

In their preparation for the party, Lady Capulet and Nurse are talking about Juliet- see Act I Scene III. Here, Nurse mentions that Juliet was born on the day before Lammas-tide, which is "a fortnight and odd days" away. This means that it is just over two weeks until Juliet's birthday. Since the introduction of the Gregorian calendar, Lammas has been celebrated on the first day of August, marking the beginning of the harvest season. With this information, we can infer that Capulet's feast is taking place in July, about two weeks prior to the first of August.