code: public long parseMillis(DateTimeParser parser, CharSequence text) {
          reset();
          return doParseMillis(DateTimeParserInternalParser.of(parser), text);
      }
docs: Parses a datetime from the given text, returning the number of
  milliseconds since the epoch, 1970-01-01T00:00:00Z.
  <p>
  This parses the text using the parser into this bucket.
  The bucket is reset before parsing begins, allowing the bucket to be re-used.
  The bucket must not be shared between threads.
  
  @param parser  the parser to use, see {@link DateTimeFormatter#getParser()}, not null
  @param text  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
  @since 2.4