code: public String getGMTOffsetDigits() {
          StringBuilder buf = new StringBuilder(_gmtOffsetDigits.length);
          for (String digit : _gmtOffsetDigits) {
              buf.append(digit);
          }
          return buf.toString();
      }
docs: Returns the decimal digit characters used for localized GMT format in a single string
  containing from 0 to 9 in the ascending order.
  
  @return the decimal digits for localized GMT format.
  @see #setGMTOffsetDigits(String)