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.

nestwiderhaken

Shows only posts, that are newer, than the day the current logged in user was created. 
This plugin is only useful if you have an other plugin installed forcing any visitor to login first. 
In that combination you get a blog in which the posts of older users are invisible for new users. 
None of the old users must therefor worry about statements made in older posts becomming available to users he don’t want. 
In the moment a user publishes a post, the amount of authorized readers for this post stays the same.

Only New Posts

Works fine.

Shows only posts, that are newer than the day the current logged in user was created.

Hide Old Posts vs Only New Posts