After your Event Name and Event Date fields are initially set in the event creation process, these fields can be updated on your RSVP form to be whatever you'd like.
To update the Event Name on your RSVP form
Go to Setup > Form Design > Right Pattern or Color - Event Name.
To update the Event Date line on your RSVP form
Go to Setup > Form Design > Right Pattern or Color - Date Line. This text can be changed to whatever you'd like (or completely removed), and doesn't have to be a date.