code: public long parseMillis(String text) {
          InternalParser parser = requireParser();
          Chronology chrono = selectChronology(iChrono);
          DateTimeParserBucket bucket = new DateTimeParserBucket(0, chrono, iLocale, iPivotYear, iDefaultYear);
          return bucket.doParseMillis(parser, text);
      }
docs: Parses a datetime from the given text, returning the number of
  milliseconds since the epoch, 1970-01-01T00:00:00Z.
  <p>
  The parse will use the ISO chronology, and the default time zone.
  If the text contains a time zone string then that will be taken into account.
  
  @param text  the text to parse, not null
  @return parsed value expressed in milliseconds since the epoch
  @throws UnsupportedOperationException if parsing is not supported
  @throws IllegalArgumentException if the text to parse is invalid