docs: public Calendar toCalendar(TimeZone zone, Locale locale) {
  		if (null == locale) {
  			locale = Locale.getDefault(Locale.Category.FORMAT);
  		}
  		final Calendar cal = (null != zone) ? Calendar.getInstance(zone, locale) : Calendar.getInstance(locale);
  		cal.setFirstDayOfWeek(firstDayOfWeek.getValue());
  		cal.setTime(this);
  		return cal;
  	}