Publishing later
A record is visible once its publish date has passed. Set the date in the future and the record stays hidden until that moment, then appears by itself: nothing needs saving when the time comes. Pages, blogs and blog posts, books, units and book pages, FAQ questions and product descriptions can all be scheduled this way.
Use it for an announcement that must not appear early, a launch at a fixed time, or a page you want ready in advance.
Taking content down at a set time
Pages and books can also carry an unpublish date: once it passes, the record is unpublished automatically. The admin has no field for it; a developer sets it through the API. In the admin, take content down by unpublishing it when the time comes.
Time zones
Dates are entered and shown in the time zone set for the site, not your computer's. "9:00" on the site means 9:00 in the site's time zone, wherever you are when you set it. If you work in another time zone, convert before you schedule, and schedule a little early when the exact minute matters.