code: final String excludeQuoted(final String datePattern) {
      final Pattern pattern = Pattern.compile("'('{2}|[^'])+'");
      final Matcher matcher = pattern.matcher(datePattern);
      final StringBuffer buffer = new StringBuffer();
      while (matcher.find()) {
        matcher.appendReplacement(buffer, "");
      }
      matcher.appendTail(buffer);
      LogLog.debug("DatePattern reduced to " + buffer.toString()
          + " for computation of time-based rollover strategy (full pattern"
          + " will be used for actual roll-file naming)");
      return buffer.toString();
    }
docs: Strips out quoted sections from a date format pattern to leave us with only
  characters meant to be interpreted by (or which are reserved by)
  {@link java.text.SimpleDateFormat}.
  
  @param datePattern
  The full pattern specified by the appender config.
  @return The datePattern minus quoted sections.
  @see java.text.SimpleDateFormat