https://api.drupal.org/api/drupal/core%21modules%21views%21src%21Plugin%21views%21argument%21FullDate.php/property/FullDate%3A%3AargFormat/10
FullDate::$argFormat | Drupal API
drupalapi
https://api.drupal.org/api/drupal/core%21modules%21datetime%21src%21Plugin%21views%21argument%21FullDate.php/class/hierarchy/FullDate/8.9.x
FullDate | Drupal API
drupalapi