code: def clear_start_date(self):
          
          if (self.get_start_date_metadata().is_read_only() or
                  self.get_start_date_metadata().is_required()):
              raise NoAccess()
          default_start_date = self._start_date_metadata['default_date_time_values'][0]
          self.my_osid_object_form._my_map['startDate'] = DateTime(year=default_start_date.year,
                                                                   month=default_start_date.month,
                                                                   day=default_start_date.day,
                                                                   hour=default_start_date.hour,
                                                                   minute=default_start_date.minute,
                                                                   second=default_start_date.second,
                                                                   microsecond=default_start_date.microsecond)
docs: Clears the start date.
  
          raise:  NoAccess - ``Metadata.isRequired()`` or
                  ``Metadata.isReadOnly()`` is ``true``
          *compliance: mandatory -- This method must be implemented.*