filter on last found date

It would be nice to filter on some dates.  Last found and placed date comes to mind.

The argument for last found date is as follows. In my area people go after "resurrections", caches which have not been found in over a year.  So filtering for those would be nice.  PQ's have a native mode for last found within the last 7 days.  During the winter, last found after the last major snowstorm is nice.  

Placed date is to help folks with their Jasmer challenges.