code: public Date getGeneralizedTime() throws IOException {
          if (tag != tag_GeneralizedTime) {
              throw new IOException(
                  "DerValue.getGeneralizedTime, not a GeneralizedTime: " + tag);
          }
          return buffer.getGeneralizedTime(data.available());
      }
docs: Returns a Date if the DerValue is GeneralizedTime.
  
  @return the Date held in this DER value