Sorting Announcements

I have an Announcements page which is sorted by "Created" in descending order so that the most recent messages appear at the top of the list.  My problem is that when someone posts a new message, the new message goes to the top of the list within that date.  I need to set it up so that the most recent dates go to the top of the list but the most recent time the message was posted goes to the bottom of the list for that date.  For example;

Announcements

World1             World1 World1                  2/1/2008    1:00pm
World2             World2 World2                  2/1/2008    2:00pm
World3             World3 World3                  2/1/2008    3:00pm
Hello1               Hello1 Hello1                   1/1/2008    1:00pm
Hello2               Hello2 Hello2                   1/1/2008    2:00pm

World 1,2 and 3 were posted on the same date 2/1/2008 so they go to the top of the list. World2 was posted on the 2/1/2008 at 1:00pm so it goes to second on the list. World 3 was also posted on the 2/1/2008 but it was posted later at 3:00pm so it goes to third on the list. If someone posts a message World4 also on the 2/1/2008 it will then go to fourth on the list and so on.

So the most recent dates go to the top but the most recent times go to the bottom for that particular date.

Is this possible?