code: public final void clear()
      {
          for (int i = 0; i < fields.length; ) {
              stamp[i] = fields[i] = 0; // UNSET == 0
              isSet[i++] = false;
          }
          areAllFieldsSet = areFieldsSet = false;
          isTimeSet = false;
      }
docs: Sets all the calendar field values and the time value
  (millisecond offset from the <a href="#Epoch">Epoch</a>) of
  this <code>Calendar</code> undefined. This means that {@link
  #isSet(int) isSet()} will return <code>false</code> for all the
  calendar fields, and the date and time calculations will treat
  the fields as if they had never been set. A
  <code>Calendar</code> implementation class may use its specific
  default field values for date/time calculations. For example,
  <code>GregorianCalendar</code> uses 1970 if the
  <code>YEAR</code> field value is undefined.
  
  @see #clear(int)