--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/xlsx/xlsxnumformatparser.cpp	Tue Mar 22 10:38:08 2016 +0100
@@ -0,0 +1,94 @@
+/****************************************************************************
+** Copyright (c) 2013-2014 Debao Zhang <hello@debao.me>
+** All right reserved.
+**
+** Permission is hereby granted, free of charge, to any person obtaining
+** a copy of this software and associated documentation files (the
+** "Software"), to deal in the Software without restriction, including
+** without limitation the rights to use, copy, modify, merge, publish,
+** distribute, sublicense, and/or sell copies of the Software, and to
+** permit persons to whom the Software is furnished to do so, subject to
+** the following conditions:
+**
+** The above copyright notice and this permission notice shall be
+** included in all copies or substantial portions of the Software.
+**
+** THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+** EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+** MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+** NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+** LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+** OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+** WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+**
+****************************************************************************/
+#include "xlsxnumformatparser_p.h"
+
+#include <QString>
+
+namespace QXlsx {
+
+bool NumFormatParser::isDateTime(const QString &formatCode)
+{
+    for (int i = 0; i < formatCode.length(); ++i) {
+        const QChar &c = formatCode[i];
+
+        switch (c.unicode()) {
+        case '[':
+            // [h], [m], [s] are valid format for time
+            if (i < formatCode.length()-2 && formatCode[i+2] == QLatin1Char(']')) {
+                const QChar cc = formatCode[i+1].toLower();
+                if (cc == QLatin1Char('h') || cc == QLatin1Char('m') || cc == QLatin1Char('s'))
+                    return true;
+                i+=2;
+                break;
+            } else {
+                // condition or color: don't care, ignore
+                while (i < formatCode.length() && formatCode[i] != QLatin1Char(']'))
+                    ++i;
+                break;
+            }
+
+        // quoted plain text block: don't care, ignore
+        case '"':
+            while (i < formatCode.length()-1 && formatCode[++i] != QLatin1Char('"'))
+                ;
+            break;
+
+        // escaped char: don't care, ignore
+        case '\\':
+            if (i < formatCode.length() - 1)
+                ++i;
+            break;
+
+        // date/time can only be positive number,
+        // so only the first section of the format make sense.
+        case ';':
+            return false;
+            break;
+
+        // days
+        case 'D':
+        case 'd':
+        // years
+        case 'Y':
+        case 'y':
+        // hours
+        case 'H':
+        case 'h':
+        // seconds
+        case 'S':
+        case 's':
+        // minutes or months, depending on context
+        case 'M':
+        case 'm':
+            return true;
+
+        default:
+            break;
+        }
+    }
+    return false;
+}
+
+} // namespace QXlsx