get the event start of an event that is different (in time)from the
        adjoining event, in CSV format

def get_csv_event_start(event_buffer):
    """ get the event start of an event that is different (in time)from the
        adjoining event, in CSV format """

    (start, end) = get_csv_next_event_start(0, event_buffer)
    if start < 0:
        return (-1, -1, "")

    print(event_buffer[start:end])

    tstart = event_buffer.find(",", start)
    tend = event_buffer.find(",", tstart+1)
    print(event_buffer[tstart:tend])
    last_time = event_buffer[tstart+1:tend].replace('"',"")

    while end > 0:
        (start, end) = get_csv_next_event_start(start, event_buffer)
        if end < 0:
            return (-1, -1, "")
        tstart = event_buffer.find(",", start)
        tend = event_buffer.find(",", tstart+1)
        this_time = event_buffer[tstart+1:tend].replace('"',"")
        if this_time != last_time:
            return (start, end + 1, last_time)

    return (-1, -1, "")