First off, I would avoid as much as possible making direct DB updates for entities. Drupal 8+'s entity model is tightly bound to its abstraction layers, implemented as hooks. It is considered best practice to always modify entities via the entity API. This will allow Drupal to keep all things in sync.
Now, the short answer to your question is that clearing your site's cache will likely result in the new values being displayed.
A better answer would be to script some PHP in order to iterate through all nodes and update their content creation date via entity API. I often use Drush in order to perform these types of operations. Below is an example that should suit your needs, based on the following presumption:
- You have loaded your node:date values into an array called
$new_node_dates, where the keys are NIDs and the values are Unix timestamps representing the new creation dates. See here for an example of reading a CSV file into an array. If the dates are not in a Unix timestamp format, you can use strtotime() to convert them.
The Drush statement would then be:
drush eval '$node_storage = \Drupal::entityTypeManager()->getStorage("node"); foreach($new_node_dates as $nid => $creation_date) { $node = $node_storage->load($nid); $node->created = $creation_date; $node->save(); }'
Best of luck!
