this is mostly about public content timed on the future, but not only.
In a standard Plone site if you create a top-level content is not shown on the navigation (is stil
there is an addon product that does exactly what you need:
collective.wfeffectiverange
it works by adding a cron job that looks for not yet published (effective date in the future) or expired (expiration date reached) content and apply a workflow transition in this case.
see https://pypi.python.org/pypi/collective.wfeffectiverange for more information