Traffic light Formula not working

Im trying to generate a formula in Excel 2007 that will allow me to implement a 'traffic light' system for dates on a training document at work. I need to have the cells that contain dates in the following parameters: -
less than 9 months old stay green,
9-12 months go yellow,
12+ go red.
I am aware of the now function, but is there an easier way as currently I have to add 3 layers per column in conditional formatting.

I hope there is!

Thanks in advance..............