The following links are very old posts by pg, so we can't assume the algorithms stated are still accurate. None the less, they should give you a rough idea of what was tweaked to put less weight on time.

2074 days ago

https://news.ycombinator.com/item?id=38704

908 days ago

https://news.ycombinator.com/item?id=1781417

Also, it's kinda neat to see the progression by comparing the two.