It can either wait a certain period after the post/page has been published, or it can close retroactively all comments prior to a preset date.

Installation:

Unpack and upload it to the /wp-content/plugins/ directory.
Activate the plugin through the 'Plugins' menu in WordPress.

Requirements:

· WordPress 2.8 or higher
· PHP 5.2 or higher

What's New in This Release: [ read full changelog ]

· Can now optionally specify a date on which to close comments across the board, and then to re-open them at a later date. This is useful if you are going on holiday, for example, or if you want to take an indefinite break from blogging.
· Timeout options are now hidden on the admin page when "Close comments" is deselected.