private void processStartCase() throws ParseException {
        if (commandLine.hasOption(OPTION_MESSAGE)) {
            String message = processMessage();
            Date startDate = processStartDate(false);
            if (startDate == null) {
                timeTracker.start(message);
            } else {
                timeTracker.startFrom(startDate, message);
            }
        } else {
            throwMissingOptionException("Argument message is require for start option.");
        }
    }