code: def update_date(self):
          
          for field in record_get_field_instances(self.record, '269'):
              for idx, (key, value) in enumerate(field[0]):
                  if key == "c":
                      field[0][idx] = ("c", convert_date_to_iso(value))
                      record_delete_fields(self.record, "260")
  
          if 'THESIS' not in self.collections:
              for field in record_get_field_instances(self.record, '260'):
                  record_add_field(self.record, '269', subfields=field[0])
              record_delete_fields(self.record, '260')
docs: 269 Date normalization.