Scheduler is a module that will allow you to schedule your content publication. It can unpublish them as well!
1. Download and install the module
2. Set permissions (if needed)
3. ¬†Configure the timezone and test the cron (configuration > Content Authoring >¬†Scheduler module settings)
4. Go to each content type, edit it and enable the scheduler if needed
More information and download at:¬†http://drupal.org/project/scheduler