I would prefer having new and existing clients pick from a list of available start times (chosen by the therapist) rather than using the calendar. With some therapists having both top of the hour (1:00) and half hour start times (1:30) this makes it difficult for clients to know the therapists hours when scheduling. For example, they may click on 2:00-3:00 when on that day the therapist needs that appointment to be 2:30-3:30. This would mean having to call each client and tell them the actual appointment time therefore making the convenience of the self scheduling inconvenient.