CSS Selector, entry published date as initial discovery date

[bradbeattie]

I have a CSS Selector feed set up. But each entry's published date is set to now whenever the cache expires (every hour, I believe). The same happens with other feeds. Is there any way to cache "whenever you first saw this entry's URL is its published date"?

To clarify the motivation, Feeder keeps putting the posts at the top of the timeline based on the feed's published dates.

Cross posted with spacecowboy/Feeder#693 in case the issue can be addressed on their side.