code: public Calendar toCalendar(Locale locale) {
          if (locale == null) {
              locale = Locale.getDefault();
          }
          DateTimeZone zone = getZone();
          Calendar cal = Calendar.getInstance(zone.toTimeZone(), locale);
          cal.setTime(toDate());
          return cal;
      }
docs: Get the date time as a <code>java.util.Calendar</code>, assigning
  exactly the same millisecond instant.
  The locale is passed in, enabling Calendar to select the correct
  localized subclass.
  <p>
  The JDK and Joda-Time both have time zone implementations and these
  differ in accuracy. Joda-Time's implementation is generally more up to
  date and thus more accurate - for example JDK1.3 has no historical data.
  The effect of this is that the field values of the <code>Calendar</code>
  may differ from those of this object, even though the millisecond value
  is the same. Most of the time this just means that the JDK field values
  are wrong, as our time zone information is more up to date.
  
  @param locale  the locale to get the Calendar for, or default if null
  @return a localized Calendar initialised with this datetime