Not played since filter: really working?

Hi emms-users,

I have already a small problem. In this case with the filter factory 
defined as "Not played since". If I filter my tracks with "Played since" 
and "Not played since" 30 days, I get exactly the same results... Either 
it is a problem with the way my tracks are storing the time or a problem 
with the code.

More precisely my question is: is this code working at expected?

(defun emms-filters-make-filter-not-played-within (days)
   "Make a not played since DAYS filter."
   (lambda (track)
     (funcall (emms-filters-make-filter-played-within days) track)))

Thanks in advance!

Best,