diff --git a/DateTime/DateTime.pro b/DateTime/DateTime.pro
new file mode 100644
index 0000000..68db0d9
--- /dev/null
+++ b/DateTime/DateTime.pro
@@ -0,0 +1,38 @@
+# DateTime.pro
+
+TARGET = IssueTest
+TEMPLATE = app
+
+QT += core
+QT += gui
+
+CONFIG += console
+CONFIG -= app_bundle
+
+# NOTE: You can fix value of QXlsx path of source code.
+#  QXLSX_PARENTPATH=./
+#  QXLSX_HEADERPATH=./header/
+#  QXLSX_SOURCEPATH=./source/
+include(../QXlsx/QXlsx.pri)
+
+##########################################################################
+# The following define makes your compiler emit warnings if you use
+# any feature of Qt which as been marked deprecated (the exact warnings
+# depend on your compiler). Please consult the documentation of the
+# deprecated API in order to know how to port your code away from it.
+DEFINES += QT_DEPRECATED_WARNINGS
+
+##########################################################################
+# You can also make your code fail to compile if you use deprecated APIs.
+# In order to do so, uncomment the following line.
+# You can also select to disable deprecated APIs only up to a certain
+# version of Qt.
+#DEFINES += QT_DISABLE_DEPRECATED_BEFORE=0x060000   
+# disables all the APIs deprecated before Qt 6.0.0
+
+##########################################################################
+# source code
+
+SOURCES += \
+main.cpp \
+test.cpp
diff --git a/DateTime/main.cpp b/DateTime/main.cpp
new file mode 100644
index 0000000..a302d50
--- /dev/null
+++ b/DateTime/main.cpp
@@ -0,0 +1,33 @@
+// main.cpp
+
+#include <QtGlobal>
+#include <QCoreApplication>
+#include <QtCore>
+#include <QVector>
+#include <QVariant>
+#include <QDebug> 
+
+#include <iostream>
+using namespace std;
+
+#include "xlsxdocument.h"
+#include "xlsxchartsheet.h"
+#include "xlsxcellrange.h"
+#include "xlsxchart.h"
+#include "xlsxrichstring.h"
+#include "xlsxworkbook.h"
+using namespace QXlsx;
+
+extern int test(QVector<QVariant> params);
+
+int main(int argc, char *argv[])
+{
+	QCoreApplication app(argc, argv);
+
+	QVector<QVariant> testParams;
+	int ret = test(testParams);
+    // qDebug() << "test return value : " << ret;
+
+	return 0; 
+}
+
diff --git a/DateTime/test.cpp b/DateTime/test.cpp
new file mode 100644
index 0000000..950b249
--- /dev/null
+++ b/DateTime/test.cpp
@@ -0,0 +1,179 @@
+// test.cpp
+
+#include <QtGlobal>
+#include <QCoreApplication>
+#include <QtCore>
+#include <QVector>
+#include <QVariant>
+#include <QDebug> 
+#include <QDir>
+
+#include <iostream>
+using namespace std;
+
+#include "xlsxdocument.h"
+#include "xlsxchartsheet.h"
+#include "xlsxcellrange.h"
+#include "xlsxchart.h"
+#include "xlsxrichstring.h"
+#include "xlsxworkbook.h"
+
+int test( QVector<QVariant> params );
+int test1( QVector<QVariant> params );
+int test2( QVector<QVariant> params );
+
+int test( QVector<QVariant> params )
+{
+    // return test1( params );
+    return test2( params );
+}
+
+int test1( QVector<QVariant> params )
+{
+    qDebug() << "[debug] current path : " << QDir::currentPath();
+
+    using namespace QXlsx;
+
+    Document doc;
+
+    doc.write( "A1", QVariant(QDateTime::currentDateTimeUtc()) );
+    doc.write( "A2", QVariant(double(10.5)) );
+    doc.write( "A3", QVariant(QDate(2019, 10, 9)) );
+    doc.write( "A4", QVariant(QTime(10, 9, 5)) );
+    doc.write( "A5", QVariant((int) 40000) );
+
+    qDebug() << "doc.read()";
+    qDebug() << doc.read( 1, 1 ).type() << doc.read( 1, 1 );
+    qDebug() << doc.read( 2, 1 ).type() << doc.read( 2, 1 );
+    qDebug() << doc.read( 3, 1 ).type() << doc.read( 3, 1 );
+    qDebug() << doc.read( 4, 1 ).type() << doc.read( 4, 1 );
+    qDebug() << doc.read( 5, 1 ).type() << doc.read( 5, 1 );
+    qDebug() << "\n";
+
+    qDebug() << "doc.cellAt()->value()";
+    qDebug() << doc.cellAt( 1, 1 )->value().type() << doc.cellAt( 1, 1 )->value();
+    qDebug() << doc.cellAt( 2, 1 )->value().type() << doc.cellAt( 2, 1 )->value();
+    qDebug() << doc.cellAt( 3, 1 )->value().type() << doc.cellAt( 3, 1 )->value();
+    qDebug() << doc.cellAt( 4, 1 )->value().type() << doc.cellAt( 4, 1 )->value();
+    qDebug() << doc.cellAt( 5, 1 )->value().type() << doc.cellAt( 5, 1 )->value();
+
+    doc.saveAs("datetime.xlsx");
+
+    return 0;
+}
+
+int test2( QVector<QVariant> params )
+{
+    qDebug() << "[debug] current path : " << QDir::currentPath();
+
+    using namespace QXlsx;
+
+    qDebug() << "\n\ndoc1\n";
+
+    Document doc;
+
+    doc.write( "A1", QVariant(QDateTime::currentDateTimeUtc()) );
+    doc.write( "A2", QVariant(double(10.5)) );
+    doc.write( "A3", QVariant(QDate(2019, 10, 9)) );
+    doc.write( "A4", QVariant(QTime(10, 9, 5)) );
+    doc.write( "A5", QVariant((int) 40000) );
+
+    qDebug() << "doc.read()";
+    qDebug() << doc.read( 1, 1 ).type() << doc.read( 1, 1 );
+    qDebug() << doc.read( 2, 1 ).type() << doc.read( 2, 1 );
+    qDebug() << doc.read( 3, 1 ).type() << doc.read( 3, 1 );
+    qDebug() << doc.read( 4, 1 ).type() << doc.read( 4, 1 );
+    qDebug() << doc.read( 5, 1 ).type() << doc.read( 5, 1 );
+    qDebug() << "\n";
+
+    qDebug() << "doc.cellAt()->value()";
+    qDebug() << doc.cellAt( 1, 1 )->value().type() << doc.cellAt( 1, 1 )->value();
+    qDebug() << doc.cellAt( 2, 1 )->value().type() << doc.cellAt( 2, 1 )->value();
+    qDebug() << doc.cellAt( 3, 1 )->value().type() << doc.cellAt( 3, 1 )->value();
+    qDebug() << doc.cellAt( 4, 1 )->value().type() << doc.cellAt( 4, 1 )->value();
+    qDebug() << doc.cellAt( 5, 1 )->value().type() << doc.cellAt( 5, 1 )->value();
+    qDebug() << "\n";
+
+    doc.saveAs("datetime.xlsx");
+
+    qDebug() << "\n\ndoc2\n";
+
+    Document doc2("datetime.xlsx");
+    if ( !doc2.load() )
+    {
+        qWarning() << "failed to load datetime.xlsx" ;
+        return (-1);
+    }
+    qDebug() << "\n\n";
+
+    doc2.write( "A6", QVariant(QDateTime::currentDateTimeUtc()) );
+    doc2.write( "A7", QVariant(double(10.5)) );
+    doc2.write( "A8", QVariant(QDate(2019, 10, 9)) );
+    doc2.write( "A9", QVariant(QTime(10, 9, 5)) );
+    doc2.write( "A10", QVariant((int) 40000) );
+
+    qDebug() << "doc2.read()";
+    qDebug() << doc2.read( 1, 1 ).type() << doc2.read( 1, 1 );
+    qDebug() << doc2.read( 2, 1 ).type() << doc2.read( 2, 1 );
+    qDebug() << doc2.read( 3, 1 ).type() << doc2.read( 3, 1 );
+    qDebug() << doc2.read( 4, 1 ).type() << doc2.read( 4, 1 );
+    qDebug() << doc2.read( 5, 1 ).type() << doc2.read( 5, 1 );
+    qDebug() << doc2.read( 6, 1 ).type() << doc2.read( 6, 1 );
+    qDebug() << doc2.read( 7, 1 ).type() << doc2.read( 7, 1 );
+    qDebug() << doc2.read( 8, 1 ).type() << doc2.read( 8, 1 );
+    qDebug() << doc2.read( 9, 1 ).type() << doc2.read( 9, 1 );
+    qDebug() << doc2.read(10, 1 ).type() << doc2.read(10, 1 );
+    qDebug() << "\n";
+
+    qDebug() << "doc2.cellAt()->value()";
+    qDebug() << doc2.cellAt( 1, 1 )->value().type() << doc2.cellAt( 1, 1 )->value();
+    qDebug() << doc2.cellAt( 2, 1 )->value().type() << doc2.cellAt( 2, 1 )->value();
+    qDebug() << doc2.cellAt( 3, 1 )->value().type() << doc2.cellAt( 3, 1 )->value();
+    qDebug() << doc2.cellAt( 4, 1 )->value().type() << doc2.cellAt( 4, 1 )->value();
+    qDebug() << doc2.cellAt( 5, 1 )->value().type() << doc2.cellAt( 5, 1 )->value();
+    qDebug() << doc2.cellAt( 6, 1 )->value().type() << doc2.cellAt( 6, 1 )->value();
+    qDebug() << doc2.cellAt( 7, 1 )->value().type() << doc2.cellAt( 7, 1 )->value();
+    qDebug() << doc2.cellAt( 8, 1 )->value().type() << doc2.cellAt( 8, 1 )->value();
+    qDebug() << doc2.cellAt( 9, 1 )->value().type() << doc2.cellAt( 9, 1 )->value();
+    qDebug() << doc2.cellAt(10, 1 )->value().type() << doc2.cellAt(10, 1 )->value();
+    doc2.saveAs("datetime2.xlsx");
+
+    qDebug() << "\n\ndoc3\n";
+
+    Document doc3("datetime2.xlsx");
+    if ( !doc3.load() )
+    {
+        qWarning() << "failed to load datetime2.xlsx" ;
+        return (-1);
+    }
+    qDebug() << "\n\n";
+
+    qDebug() << "doc3.read()";
+    qDebug() << doc3.read( 1, 1 ).type() << doc3.read( 1, 1 );
+    qDebug() << doc3.read( 2, 1 ).type() << doc3.read( 2, 1 );
+    qDebug() << doc3.read( 3, 1 ).type() << doc3.read( 3, 1 );
+    qDebug() << doc3.read( 4, 1 ).type() << doc3.read( 4, 1 );
+    qDebug() << doc3.read( 5, 1 ).type() << doc3.read( 5, 1 );
+    qDebug() << doc3.read( 6, 1 ).type() << doc3.read( 6, 1 );
+    qDebug() << doc3.read( 7, 1 ).type() << doc3.read( 7, 1 );
+    qDebug() << doc3.read( 8, 1 ).type() << doc3.read( 8, 1 );
+    qDebug() << doc3.read( 9, 1 ).type() << doc3.read( 9, 1 );
+    qDebug() << doc3.read(10, 1 ).type() << doc3.read(10, 1 );
+    qDebug() << "\n";
+
+    qDebug() << "doc3.cellAt()->value()";
+    qDebug() << doc3.cellAt( 1, 1 )->value().type() << doc3.cellAt( 1, 1 )->value();
+    qDebug() << doc3.cellAt( 2, 1 )->value().type() << doc3.cellAt( 2, 1 )->value();
+    qDebug() << doc3.cellAt( 3, 1 )->value().type() << doc3.cellAt( 3, 1 )->value();
+    qDebug() << doc3.cellAt( 4, 1 )->value().type() << doc3.cellAt( 4, 1 )->value();
+    qDebug() << doc3.cellAt( 5, 1 )->value().type() << doc3.cellAt( 5, 1 )->value();
+    qDebug() << doc3.cellAt( 6, 1 )->value().type() << doc3.cellAt( 6, 1 )->value();
+    qDebug() << doc3.cellAt( 7, 1 )->value().type() << doc3.cellAt( 7, 1 )->value();
+    qDebug() << doc3.cellAt( 8, 1 )->value().type() << doc3.cellAt( 8, 1 )->value();
+    qDebug() << doc3.cellAt( 9, 1 )->value().type() << doc3.cellAt( 9, 1 )->value();
+    qDebug() << doc3.cellAt(10, 1 )->value().type() << doc3.cellAt(10, 1 )->value();
+    doc2.saveAs("datetime2.xlsx");
+
+    return 0;
+}
+