* @param to the end time in HH:MM format
     * @param days comma-separated list of days (1=Sunday, 7=Saturday)
     * @param delay the delay in milliseconds to apply during this interval
     */
    public void addIntervalRule(final String from, final String to, final String days, final long delay) {
        ruleList.add(new IntervalRule(from, to, days, delay));
    }

    /**
     * Checks if the crawler is currently running.
     *