@Override
        public int estimateLength() {
            int max = 0;
            for (int i=mValues.length; --i >= 0; ) {
                int len = mValues[i].length();
                if (len > max) {
                    max = len;
                }
            }
            return max;
        }
Returns an estimate for the maximum length date that this date
formatter will produce. The actual formatted length will almost always
be less than or equal to this amount.
@return an estimate of the maximum length
xmppserver/src/main/java/org/jivesoftware/util/FastDateFormat.java