code: public final void clear(int field)
      {
          fields[field] = 0;
          stamp[field] = UNSET;
          isSet[field] = false;
  
          areAllFieldsSet = areFieldsSet = false;
          isTimeSet = false;
      }
docs: Sets the given calendar field value 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(field)} will return <code>false</code>, and
  the date and time calculations will treat the field as if it
  had never been set. A <code>Calendar</code> implementation
  class may use the field's specific default value for date and
  time calculations.
  
  <p>The {@link #HOUR_OF_DAY}, {@link #HOUR} and {@link #AM_PM}
  fields are handled independently and the <a
  href="#time_resolution">the resolution rule for the time of
  day</a> is applied. Clearing one of the fields doesn't reset
  the hour of day value of this <code>Calendar</code>. Use {@link
  #set(int,int) set(Calendar.HOUR_OF_DAY, 0)} to reset the hour
  value.
  
  @param field the calendar field to be cleared.
  @see #clear()