I wrote this blog-post & essay/paper about HN a couple of weeks back. My finding was that there is not really a best time to post (in general, rather than asking questions) in terms of the number of replies you would get (but I only have looked at it starting the moment posts reach the front page):

http://foundation.logilogi.org/2011/5/9/the-best-time-to-pos...

During busy times thread-churn is higher, but more people read them and reply, while during low activity times threads stay on longer but are read and replied to by about the same number of people, just over a longer period of time.

This has been discussed a bunch of time before (though I'm sure the answer changes!) Here's my favourite answer: http://news.ycombinator.com/item?id=1758554

And I'm sure there was a related blog post where he discussed title lengths (< 40 == good) and such, but I can't dig it up... anyone?

Statistics on when posts are submitted can be found here:

http://blog.itlater.com/whats-the-best-time-to-post-to-hacke...

From that, take what you will.

thanks so much guys

Depends, I'm guessing you want to target the valley? Perhaps around 3 EST for a nice geographical spread (much later and much of Europe is hugging their teddybears).

thanks I needed this too :)