Publish On...
"Publish On..." gives you the room to plan ahead for future events, sales, etc., that you might require special content for. You can create the content, set a date and time, and forget about it. When the right day comes along, the content will publish itself.
Setting a "Publish On..." Time

Once you have created and saved the content you'd like to publish at a certain time, you can set the desired publish date and time. Click the "Save" button and then the "Publish On..." option.

Select a publish date and time. NOTE: there can be a slight delay between the scheduled time and the actual publish time. For instance, if you set it to start at 8:00 am, the page will become published and available for users to see within 10 minutes of 8:00 am.
Click the "Schedule Publish" button when you're ready.
The version of the page that will be published when the "Publish On..." date comes about will be the most current saved version of the page. So, if you make more changes to the page after you have set a "Publish On..." date, those changes will also be included when the page is published.
If you manually publish a page after you have set a "Publish On..." date, but before that date comes about, the "Publish On..." date you created will be cleared from the system. You would need to set a new date and time if you want to schedule another publish.
Canceling a "Publish On..." Date and Time

You can cancel a "Publish On..." date and time by clicking the "Save" button and then clicking the "Cancel" button next to the "Publish On..." information.
Keep time zone differences in mind when setting the "Publish On..." time. The time that is set will be based in your local time zone. So, for instance, if you are in the Central time zone, and you set the publish time to 8:00am, it will publish at 8:00am Central, which will be 9:00am Eastern, etc.