Improve the QDate support

src/xlsx/xlsxutility.cpp

@@ -77,7 +77,7 @@ QDateTime datetimeFromNumber(double num, bool is1904)
     if (!is1904 && num > 60)
         num = num - 1;
 
-    qint64 msecs = static_cast<qint64>(num * 1000*60*60*24.0);
+    qint64 msecs = static_cast<qint64>(num * 1000*60*60*24.0 + 0.5);
     QDateTime epoch(is1904 ? QDate(1904, 1, 1): QDate(1899, 12, 31), QTime(0,0));
 
     return epoch.addMSecs(msecs);

src/xlsx/xlsxworkbook.cpp

@@ -53,7 +53,7 @@ WorkbookPrivate::WorkbookPrivate(Workbook *q) :
 
     strings_to_numbers_enabled = false;
     date1904 = false;
-    defaultDateFormat = QStringLiteral("yyyy-mm-ddThh:mm:ss");
+    defaultDateFormat = QStringLiteral("yyyy-mm-dd");
     activesheet = 0;
     firstsheet = 0;
     table_count = 0;

src/xlsx/xlsxworksheet.cpp

@@ -49,6 +49,7 @@
 #include <QXmlStreamReader>
 
 #include <stdint.h>
+#include <math.h>
 
 QT_BEGIN_NAMESPACE_XLSX
 
@@ -516,6 +517,8 @@ QVariant Worksheet::read(int row, int column) const
         QDateTime dt = cell->dateTime();
         if (val < 1)
             return dt.time();
+        if (fmod(val, 1.0) <  1.0/(1000*60*60*24)) //integer
+            return dt.date();
         return dt;
     }
     return cell->value();
@@ -848,8 +851,8 @@ int Worksheet::writeDateTime(int row, int column, const QDateTime &dt, const For
     if (d->checkDimensions(row, column))
         return -1;
 
-    Format fmt = format;
-    if (!fmt.isValid())
+    Format fmt = format.isValid() ? format : d->cellFormat(row, column);
+    if (!fmt.isValid() || !fmt.isDateTimeFormat())
         fmt.setNumberFormat(d->workbook->defaultDateFormat());
     d->workbook->styles()->addXfFormat(fmt);
 
@@ -882,8 +885,8 @@ int Worksheet::writeTime(int row, int column, const QTime &t, const Format &form
     if (d->checkDimensions(row, column))
         return -1;
 
-    Format fmt = format;
-    if (!fmt.isValid())
+    Format fmt = format.isValid() ? format : d->cellFormat(row, column);
+    if (!fmt.isValid() || !fmt.isDateTimeFormat())
         fmt.setNumberFormat(QStringLiteral("hh:mm:ss"));
     d->workbook->styles()->addXfFormat(fmt);