How can I schedule in advance an update to a node, to occur at a given time?
This could be done with a Rules Schedule:


  The Rules module allows site administrators to define conditionally
  executed actions based on occurring events (known as reactive or ECA
  rules). It's a replacement with more features for the trigger module
  in core and the successor of the Drupal 5 workflow-ng module.


specifically this functionality: Flexible scheduling system that allows scheduling any component / action.