For the people who still are getting confused about the time/date thing, here is a bit of a different explanation.
On your Dashboard, go to Settings, then Formatting. The fourth option down is Timestamp Format. You need to change this so it will show the day and NOT the time at all. The time already shows up at the bottom of your post in a seperate area.
So basically, change it to the option that says “Tuesday, April 14, 2009” or whatever the current date is. If you set it to one that shows the time, it will still show up as Undefined on your site.
Hope this helps. 🙂