Resolves: tdf#100822 use sax::Converter::parseDateTime() for 'd' ISO 8601 date

Instead of squeezing the string through the locale dependent
number parser (which should force '.' Time100SecSeparator for 'T'
ISO 8601 but apparently doesn't yet) that is a bottle neck anyway.

Change-Id: I70f74e680322a715c9cc658c8be033620d9798e3

sc/source/filter/oox/sheetdatabuffer.cxx

@@ -48,6 +48,7 @@
 #include "documentimport.hxx"
 #include "formulabuffer.hxx"
 #include <numformat.hxx>
+#include <sax/tools/converter.hxx>
 
 namespace oox {
 namespace xls {
@@ -206,15 +207,17 @@ void SheetDataBuffer::setErrorCell( const CellModel& rModel, sal_uInt8 nErrorCod
 
 void SheetDataBuffer::setDateCell( const CellModel& rModel, const OUString& rDateString )
 {
-    ScDocument& rDoc = getScDocument();
-    SvNumberFormatter* pFormatter = rDoc.GetFormatTable();
-
-    double fValue = 0.0;
-    sal_uInt32 nFormatIndex = 0;
-    bool bValid = pFormatter->IsNumberFormat( rDateString, nFormatIndex, fValue );
+    css::util::DateTime aDateTime;
+    if (!sax::Converter::parseDateTime( aDateTime, nullptr, rDateString))
+    {
+        SAL_WARN("sc.filter", "SheetDataBuffer::setDateCell - could not parse: " << rDateString);
+        // At least don't lose data.
+        setStringCell( rModel, rDateString);
+        return;
+    }
 
-    if(bValid)
-        setValueCell( rModel, fValue );
+    double fSerial = getUnitConverter().calcSerialFromDateTime( aDateTime);
+    setValueCell( rModel, fSerial);
 }
 
 void SheetDataBuffer::createSharedFormula(const ScAddress& rAddr, const ApiTokenSequence& rTokens)