private StringBuffer applyRules(Calendar calendar, StringBuffer buf) {
        Rule[] rules = mRules;
        int len = mRules.length;
        for (int i=0; i<len; i++) {
            rules[i].appendTo(buf, calendar);
        }
        return buf;
    }
@param pattern {@link java.text.SimpleDateFormat} compatible pattern
@param timeZone optional time zone, overrides time zone of formatted
date
@param locale optional locale, overrides system locale
@param symbols optional date format symbols, overrides symbols for
provided locale
xmppserver/src/main/java/org/jivesoftware/util/FastDateFormat.java