Added callback to default to current date

But it isn't displaying, possibly because of having the wrong kind of widget

modules/opencase_entities/opencase_entities.install

@@ -1,5 +1,15 @@
 <?php
 
+function opencase_entities_update_8013() {
+  $update_manager = \Drupal::entityDefinitionUpdateManager();
+  $definition = $update_manager->getFieldStorageDefinition('activity_date_time', 'oc_activity');
+ // $definition->setDescription('');
+ // $definition->setRequired('');
+      //->setDefaultValueCallback('Drupal\opencase_entities\Entity\OCActivity::currentDateTime')
+  $update_manager->updateFieldStorageDefinition($definition);
+}
+
+
 /**
  * Add 'activity_date_time' field to 'oc_activity' entities.
  */