Post Category Child/Grandchild Displayed Differently

Hi all :),

1)

I’m making a news site and I want to organize it in a way that:
a) Each day’s posts of a particular section (e.g. Politics, Finance, etc.) are grouped together.
b) The grouped together daily posts display one way, whereas the archive of monthly posts display a different way.

The way that I have it so far is:

Parent (Category) -> Child (Category) -> Grandchild (Category) -> Great Grandchild (Category) -> Post

e.g.
Finance -> 2012 -> September -> 9 -> Euro Falls to an All New Low
Finance -> 2012 -> September -> 9 -> Housing Boom Leads to New Opportunities
Finance -> 2012 -> September -> 9 -> Gold Prices Skyrocket

Politics -> 2012 -> September -> 9 -> Obama Resigns
Politics -> 2012 -> September -> 9 -> Antarctica Declares Independence
Politics -> 2012 -> September -> 9 -> World Peace Treaty Established

I want to make it so that on http://www.domain.com only today’s politics posts will be displayed, and moreover that ALL of today’s politics posts will be displayed (regardless of how many). However, I only want to display the headline of each post along with that post’s respective picture in a grid-like format (users can then click on any of the headlines to be taken to that post’s page).

The post’s link structure, in all cases, will simply be http://www.domain.com/post-name.

The part I’m finding tricky is how can I make it so that this Great Grandchild category displays in this fashion (grid-like format showing only post headline and thumbnail), but make the Child and Grandchild categories display differently (mere lists)?

Or should I be doing this a different way instead of using post categories, or some other way?

Someone suggested to me that instead of making date categories as I have above, to use the existing publish dates already associated with each post. Is that a better way, and if so how about if I want to see the posts for the day of August 24, for example? How would I let the user query that with the lack of its own category? Or would I simply make one post per day (e.g. 2012-09-09) which includes in that post the headlines and thumbnails of all posts posted on that date?

2)

I also don’t know which of the following two category structures are better:

Finance -> 2012 -> September -> 9 -> Post
Politics -> 2012 -> September -> 9 -> Post

or

2012 -> September -> 9 -> Finance -> Post
2012 -> September -> 9 -> Politics -> Post

Thanks!

I’m really trying to figure this out. It seems to me that maybe what was suggested to me of using the dates associated with posts is better than the method I had in mind, but does this mean I should still make one post per day which includes all of that day’s posts within it?