How can I create a script to list the time certain files are not being used?

example:

Name ......... Modification
aa.txt ....... 07/11/2012
aabb.txt ..... 07/11/2012
bb.txt ....... 07/10/2011
cc.txt ....... 07/09/2010
ccdd.txt ..... 07/09/2010

result
Recently: 2 File
1 Year: 1 File
2 Years: 2 File
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