You can configure a publication Schedule for media under the Security section of single media page for specific media. If configured, the Publication Schedule overrides other means of publication, ensuring that the player will not present the video outside of the defined time frame.
When the Publish date is in the future, the player will display a countdown to when the video will be available as displayed in the screenshot below.
When the Unpublish date is in the past, the player will say "This video is no longer available" as shown in screenshot below.
Note that the text displayed in the player may differ based on what player language that is configured on your account under Settings -> Player -> Language.