How to shift/change timestamp in a scheduled rule?
Yes, the timestamp of when the task is to be scheduled is stored in rules_scheduler db table, in date field. You can run a query like:

db_update('rules_scheduler')
  -&gt;expression('date', 'date + 86400') // 86400 = 24 * 60 * 60
  -&gt;condition('tid', $your_task_id)
  -&gt;execute();