docs: private final int skip_timestamp_past_digits(int min, int max)
          throws IOException
      {
          int c;
  
          // scan the first min characters insuring they're digits
          while (min > 0) {
              c = read_char();
              if (!IonTokenConstsX.isDigit(c)) {
                  error("invalid character '"+(char)c+"' encountered in timestamp");
              }
              --min;
              --max;
          }
          // stop at the first non digit between min and max
          while (max > 0) {
              c = read_char();
              if (!IonTokenConstsX.isDigit(c)) {
                  return c;
              }
              --max;
          }
          // max characters reached; stop
          return read_char();
      }