I had this issue in the last version of WordPress 2.7 and hoped that this simple - yet crucial - feature would be fixed; however, sadly it has not.
I posted this about WordPress 2.7 in an earlier support topic, but because this is still occuring I thought I'd start a new topic to see who is having issues with the TimeStamp not working in 2.71.
I'm getting so frustrated with this because I can't be on to publish posts at all time. I want to be able to just schedule it and forget it.
Any ideas? Or did they not bother fixing this issue in 2.71 and it's on hold until the next version now?