docs: public static String dateFormat(String dateStr, String fromFormat, String toFormat, TimeZone tz) {
  		SimpleDateFormat fromFormatter = FORMATTER_CACHE.get(fromFormat);
  		fromFormatter.setTimeZone(tz);
  		SimpleDateFormat toFormatter = FORMATTER_CACHE.get(toFormat);
  		toFormatter.setTimeZone(tz);
  		try {
  			return toFormatter.format(fromFormatter.parse(dateStr));
  		} catch (ParseException e) {
  			LOG.error("Exception when formatting: '" + dateStr +
  				"' from: '" + fromFormat + "' to: '" + toFormat + "'", e);
  			return null;
  		}
  	}