If you want to test it our yourself do this
1) Make a search on google
eg.
http://www.google.com/search?hl=en&q=digg&btnG=Search&meta=
2) add
&as_qdr=y
to your URL
eg.
http://www.google.com/search?hl=en&q=digg&btnG=Search&meta=&as_qdr=y
&as_qdr=y——-> last year
&as_qdr=m3——-> last 3 months
&as_qdr=m6——-> last 6 months
&as_qdr=all———> all results