Bill Erickson

When editing a post, check “Mark as Old” in the metabox labeled “Old Post Notification” to add the notification to the top of the post. You can also define a custom message for this specific post. If no custom message is provided, the default message set in Settings > Old Post Notification will be used.
Further Customization with filters, described in documentation.
<a href="https://github.com/billerickson/old-post-notification/wiki" rel="nofollow ugc">Documentation</a> | <a href="https://github.com/billerickson/old-post-notification/issues" rel="nofollow ugc">Support Forum</a>

Old Post Notification

Mark posts as old and display a notification message above the content.

Jan Štětina

Hides posts older than given date or amount of time relative to present (see <code>(http://php.net/manual/en/function.strtotime.php strtotime)</code>).
You can also choose a capability – users who have this capability will then see all posts. And if you enter <code>none</code>, even admins will be excluded.
Uses <code>posts_where</code> and <code>getarchives_where</code> filters.
Developed for private use, but has perspective for more extensive usage. I can’t guarantee any support in the future nor further development, but it is to be expected. Kindly inform me about bugs, if you find any, or propose new features: zaantar@zaantar.eu.

Hide Old Posts

Hides posts older than given amount of time.

Old Post Notification vs Hide Old Posts