How can I get all feed entries from a page like Google Reader? (Since RSS is transitory)

I'm trying to build a scri开发者_Go百科pt to retrieve all feed entries from a given page, but I can get only the most recents. How does Google Reader do it?

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I'm pretty sure they just store it. Once someone adds it to their list, Google Reader starts archiving and saving each entry.

If you find an obscure feed, you'll find it can't go back since before you started using it.

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Most feed-generating scripts are programmed to only include a specified number of entires, say the ten most recent posts to a blog. Google reader does, as was said before, download and archive all new posts from each unique feed in its users' readers. That's why you can view older materials on it.

If the page is your own, you could try increasing the number of entires included in the RSS feed. Otherwise, there is no way to retrieve entries from a page via RSS if those entries are no longer available in the feed.