To list all files that were modified between 2009 and 2011, use find with -newermt:

 find . -type f -newermt '01 jan 2009 00:00:00' -not -newermt '01 jan 2012 00:00:00' -ls

To remove:

find . -type f -newermt '01 jan 2009 00:00:00' -not -newermt '01 jan 2012 00:00:00' -delete