Conditional Formatting of Cells in Excel 2010

I have a spreadsheet for training that I want the dates to change to red when it's less than or equal to 90 days from the date that is entered in the cell. I used the Conditional Formatting that is in Excel 2010. Everyone tells me it should work, but no one seems to know why it's not. It changes everything to red. I even tried "" around the ="TODAY()-275", but that changed all of the dates red. This is what I did:

I highlighted the cells that I wanted to format.
I clicked on Conditional Formatting on the thread.
I clicked on "Format only cells that contain".
Clicked on the Drop Down Box and Chose "Cell Value".
Clicked on the Drop Down Box and Chose "less than or equal to".
I type in [=TODAY()-275].
Clicked on the Format button.
I changed the color to Red.

My spreadsheet has the following columns in it:
2/11/2012 3/11/2013 4/10/2013 6/11/2013 12/31/2012

It changed the 2/11/2012 to red and left the others black. It should have turned 2/11/2012 and 12/31/2012 red. Since today's date is 12/03/2012, I figure anything between today and 3/2/2013 would change to red.

I can't understand why it's not working correctly. Any help in this would be greatly appreciated!!!