If you want to create announcements to post at a certain date and time, follow these steps.
Click the Announcements link.
Type a title for the Announcement in the title field [1] and add content in the Rich Content Editor [2]. Click the Delay posting checkbox [3].
Select the Calendar icon and set the date and time using the calendar tool [1]. Or manually enter a date and time.
Click the Save button to post the announcement.
Once you add the Announcement, it will show up on the Announcements page. However, since you delayed the posting, it will have the reminder that "This topic will not be visible to users until DATE at TIME." [1]