Someone was wondering this today, and we used to be able to change all that many moons ago. Now I can't see how. I went to my profile, but it isn't there.
I haven't been around forever but looked for a way some time ago and didn't find one. I just found out in another forum that no matter where you live your post is timed from the Eastern time zone which would explain why I'm always posting 3 hours later than I think I am.