This has been discussed many times - have you searched for an answer? If you're really a hacker, why not do some research and tell us your findings.
Define "best".
Look at the new page. If the time on the last story is at least an hour ago, then it is probably a fine time to submit. Generally you want more time on the new page (since that is your only hope to get up votes at first).
It depends on the story. If it's specific to Silicon Valley, weekday mornings (Pacific Time) are often best. Political or somewhat off-topic? over the weekend. General scienceNighttime in the Pacific.
The best time is when you find something interesting that the community might like.
The worst time is optimized for treating HN like it's just a traffic source.
You're right - but what happens when you have something interesting that the community might like - but there's no one to online to vote it up so that everyone see it!