How can I limit feeds in Google Reader?

I don’t believe there is a way to go under a day. Right now, there is no capability for extensions in Google Reader, so you can’t write a script to adjust it; there is also no Labs function, so there isn’t any chance of a developer solution. Your best bet would be to start with the newest items first and read until you see articles that are six hours or older. Also, depending on the website, there are options you can add to the end of the url (Gawker websites have this) that will adjust what content comes in so you can cut out some of the content in your feeds, reducing the number of items to a more manageable amount.

Within Google Reader, there is no option to automatically delete things that’re old.

However, You can manually go in each day and, at the top of that window, click “Mark all as read” (after you’ve read what you want), or delete items older than 1 day/1 week/2 weeks.