I reproduced in Vista as follows (with all three date columns activated):
1. Search C:\Users\Owner\AppData\Roaming\Microsoft\Windows\Recent\ for *.lnk with no other tabs activated.
2. Note the date range (I found 184 files with dates from 4/12/2008 to 4/22/2008).
3. Then activate the Search by date tab with a date of 4/13/2008 and use "before." Start the tool (multiple times, once for each date choice). Result: all three of the date choices produce a blank list. Several files have dates of 4/12/2008.
4. Using "after," all three date choices produce a list with all 184 files -- dates of 4/12/2008 and 4/13/2008 show, but they should not. I guess "after" doesn't work either …
5. Using "on," all three date choices produce a blank list. Several files have dates of 4/13/2008.
6. 22 files have dates within the last 4 hours. Using "within 8 hours," I get lists of 20 to 22 items, so this part of the feature seems to work …