Hi Elizabeth - it sounds like the issue is with the sampling and not the filtering.
What sample method are you using?
If you always only need the current year could you filter your Oracle query with something like
WHERE EXTRACT(YEAR FROM D.CALENDAR_DATE) = EXTRACT(YEAR FROM SYSDATE)
instead of filtering in Prep?
Have a good one!
could be a problem with the Date filter, don´t recognized the format Date.
What is the version from Tableau Prep?