time at which you post influence the ability to reach front page.

* You can find an explanation from pg here : http://news.ycombinator.com/item?id=38704

* There was a post discussing rankings in reddit/delicious/HN here : http://news.ycombinator.com/item?id=234749

* There are other posts discussing specifically the HN algorithm with answers from PG : http://news.ycombinator.com/item?id=1781013

* And you can use the tool HNPickup to tell you if it's a good time to post or not : http://hnpickup.appspot.com/