I would like the cached pages to be deleted at a specific date. How is it possible to specify that date? In my case, I need the dates to be dynamically set for each page.
You can't. Once the pages are on the client, the client is in control of when they're deleted. If you update the manifest file at the specific dates, removing the relevant files, then when the browser next connects to your site and replaces the application cache those files will not be downloaded.