This project provides you to publish the revisions of a content when it reaches a specific state.
States in this module is got through the workbench moderation States. For this, you have to create a timestamp field with machine name field_publish_on.
The admin form link is provided to select a state. Once you select a state and the content reaches that state. Whenever the cron will run , it will get all the revisions which are in that state and whose publish_on time is less than the cron execution time and it published them.