Resolves: tdf#92767 use ISO 8601 for internal date string representation

Change-Id: I481bf3295feb64827de2122234a9300d0b8ced40
(cherry picked from commit 3e17ed1f)
Reviewed-on: https://gerrit.libreoffice.org/17172Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Michael Meeks <michael.meeks@collabora.com>
Tested-by: Michael Meeks <michael.meeks@collabora.com>

sc/source/core/data/column3.cxx

@@ -2020,6 +2020,10 @@ class FilterEntriesHandler
             fVal = rtl::math::approxFloor(fVal);
             mbHasDates = true;
             bDate = true;
+            // Convert string representation to ISO 8601 date to eliminate
+            // locale dependent behaviour later when filtering for dates.
+            sal_uInt32 nIndex = pFormatter->GetFormatIndex( NF_DATE_DIN_YYYYMMDD);
+            pFormatter->GetInputLineString( fVal, nIndex, aStr);
         }
         // maybe extend ScTypedStrData enum is also an option here
         mrStrings.push_back(ScTypedStrData(aStr, fVal, ScTypedStrData::Value,bDate));