code: public static String dateFormat(long ts, String format, TimeZone tz) {
  		SimpleDateFormat formatter = FORMATTER_CACHE.get(format);
  		formatter.setTimeZone(tz);
  		Date dateTime = new Date(ts);
  		return formatter.format(dateTime);
  	}
docs: Format a timestamp as specific.
  @param ts the timestamp to format.
  @param format the string formatter.
  @param tz the time zone