def calculate_appointments(new_set, old_set):
    """
    Calculate different appointment types.  
    Used for making useful distinctions in the email message.

    new_set will be the fresh set of all available appointments at a given interval
    old_set will the previous appointments variable getting passed in.

    Ex1: Addition of HONEOYE
    new_set = {'LIVERPOOL', 'BROOKLYN', 'HONEOYE', 'KINGSTON'}
    old_set = {'LIVERPOOL', 'BROOKLYN', 'KINGSTON'}
    returns ->->
    new_appointments = {'HONEOYE'}
    all_appointments = {'LIVERPOOL', 'BROOKLYN', 'KINGSTON', HONEOYE}

    Ex2: No Changes
    new_set = {'LIVERPOOL', 'BROOKLYN', 'HONEOYE', 'KINGSTON'}
    old_set = {'LIVERPOOL', 'BROOKLYN', 'HONEOYE', 'KINGSTON'}
    returns ->->
    new_appointments = set() (empty set)
    all_appointments = {'LIVERPOOL', 'BROOKLYN', 'HONEOYE', 'KINGSTON'}

    """

    new_appointments = new_set.difference(old_set)          # set of All appointments minus set of Old appointments yields the set of New appointments
    old_appointments = new_set.intersection(old_set)        # New intersect Old. yields those appointments that  (intersect is equivalent the overlap in a venn diagram)
    return new_appointments, old_appointments               # Return new sets