def _parse_ical_string(ical_string):
    """
    SU,MO,TU,WE,TH,FR,SA
    DTSTART;TZID=America/New_York:20180804T233251\nRRULE:FREQ=WEEKLY;BYDAY=SA
    DTSTART;TZID=America/New_York:20180804T233251\nRRULE:FREQ=DAILY
    DTSTART;TZID=America/New_York:20180804T233251\nRRULE:FREQ=WEEKLY;BYDAY=MO,TU,WE,TH,FR,SA
    DTSTART;TZID=America/New_York:20180718T174500
    """
    start_time = ical_string.splitlines()[0].replace(DTSTART, '')
    if "RRULE" in ical_string:
        days = ical_string.splitlines()[1].replace(REPEAT, '')
        if days == "RRULE:FREQ=DAILY":
            days = ['DAILY']
        else:
            days = days.split(',')
    else:
        days = None
    start_time = start_time.splitlines()[0].split(':')[1]
    datetime_object = datetime.strptime(start_time, '%Y%m%dT%H%M%S')
    return datetime_object, days