The same problem exists in Photoshop Elements. Seems to be an "oversight".
Really it seems pretty sad that a date sort wouldn't include time as important as that is in photography.
In Photoshop Elements 7.0, we have this option. Not sure about earlier versions.
1. In Organizer, Go to Edit -> Preferences.
2. Select Show Newest First within Each Day Radio button.
3. Click OK.
This will solve the problem.