code: def update_date(self):
          
          dates_269 = record_get_field_instances(self.record, '269')
          for idx, field in enumerate(dates_269):
              new_subs = []
              old_subs = field[0]
              for code, value in old_subs:
                  if code == "c":
                      new_subs.append((
                          "c",
                          convert_date_from_iso_to_human(value)
                      ))
                  else:
                      new_subs.append((code, value))
              dates_269[idx] = field_swap_subfields(field, new_subs)
docs: 269 Date normalization.