code: protected int convertText(String text, Locale locale) {
          return GJLocaleSymbols.forLocale(locale).dayOfWeekTextToValue(text);
      }
docs: Convert the specified text and locale into a value.
  
  @param text  the text to convert
  @param locale  the locale to convert using
  @return the value extracted from the text
  @throws IllegalArgumentException if the text is invalid