XLSX Date Support / Test + Fix for years beyond 2037

This also fixes years < 1902 on 32-bit PHP systems.

src/Spout/Reader/XLSX/Helper/CellValueFormatter.php

@@ -28,7 +28,6 @@ class CellValueFormatter
     const XML_ATTRIBUTE_STYLE_ID = 's';
 
     /** Constants used for date formatting */
-    const NUM_DAYS_FROM_JAN_1_1900_TO_JAN_1_1970 = 25569; // actually 25567 but accommodating for an Excel bug with some bisextile years
     const NUM_SECONDS_IN_ONE_DAY = 86400;
 
     /**
@@ -183,17 +182,26 @@ class CellValueFormatter
      */
     protected function formatExcelTimestampValue($nodeValue)
     {
-        $numDaysSince1970Jan1 = $nodeValue - self::NUM_DAYS_FROM_JAN_1_1900_TO_JAN_1_1970;
-
         // Fix for the erroneous leap year in Excel
-        if ($nodeValue < self::ERRONEOUS_EXCEL_LEAP_YEAR_DAY) {
-            $numDaysSince1970Jan1++;
+        if (ceil($nodeValue) > self::ERRONEOUS_EXCEL_LEAP_YEAR_DAY) {
+            --$nodeValue;
         }
 
-        $unixTimestamp = round($numDaysSince1970Jan1 * self::NUM_SECONDS_IN_ONE_DAY);
+        // The value 1.0 represents 1900-01-01. Numbers below 1.0 are not valid Excel dates.
+        if ($nodeValue < 1.0) {
+            return null;
+        }
+
+        // Do not use any unix timestamps for calculation to prevent
+        // issues with numbers exceeding 2^31.
+        $secondsRemainder = fmod($nodeValue, 1) * self::NUM_SECONDS_IN_ONE_DAY;
+        $secondsRemainder = round($secondsRemainder, 0);
 
         try {
-            $cellValue = (new \DateTime())->setTimestamp($unixTimestamp);
+            $cellValue = \DateTime::createFromFormat('|Y-m-d', '1899-12-31');
+            $cellValue->modify('+' . intval($nodeValue) . 'days');
+            $cellValue->modify('+' . $secondsRemainder . 'seconds');
+
             return $cellValue;
         } catch (\Exception $e) {
             return null;

tests/Spout/Reader/XLSX/Helper/CellValueFormatterTest.php

@@ -0,0 +1,80 @@
+<?php
+
+namespace Box\Spout\Reader\XLSX\Helper;
+
+/**
+ * Class CellValueFormatterTest
+ *
+ * @package Box\Spout\Reader\XLSX\Helper
+ */
+class CellValueFormatterTest extends \PHPUnit_Framework_TestCase
+{
+    /**
+     * @return array
+     */
+    public function dataProviderForExcelDateTest()
+    {
+        return [
+            [ CellValueFormatter::CELL_TYPE_NUMERIC, 42429, '2016-02-29 00:00:00' ],
+            [ CellValueFormatter::CELL_TYPE_NUMERIC, '146098', '2299-12-31 00:00:00' ],
+            [ CellValueFormatter::CELL_TYPE_NUMERIC, -700, null ],
+            [ CellValueFormatter::CELL_TYPE_NUMERIC, 0, null ],
+            [ CellValueFormatter::CELL_TYPE_NUMERIC, 0.5, null ],
+            [ CellValueFormatter::CELL_TYPE_NUMERIC, 1, '1900-01-01 00:00:00' ],
+            [ CellValueFormatter::CELL_TYPE_NUMERIC, 59.999988425926, '1900-02-28 23:59:59' ],
+            [ CellValueFormatter::CELL_TYPE_NUMERIC, 60.458333333333, '1900-02-28 11:00:00' ],
+        ];
+    }
+
+    /**
+     * @dataProvider dataProviderForExcelDateTest
+     *
+     * @return void
+     */
+    public function testExcelDate($cellType, $nodeValue, $expectedDateAsString)
+    {
+        $nodeListMock = $this->getMockBuilder('DOMNodeList')->disableOriginalConstructor()->getMock();
+
+        $nodeListMock
+            ->expects($this->atLeastOnce())
+            ->method('item')
+            ->with(0)
+            ->will($this->returnValue((object)[ 'nodeValue' => $nodeValue ]));
+
+        $nodeMock = $this->getMockBuilder('DOMElement')->disableOriginalConstructor()->getMock();
+
+        $nodeMock
+            ->expects($this->atLeastOnce())
+            ->method('getAttribute')
+            ->will($this->returnValueMap([
+                [ CellValueFormatter::XML_ATTRIBUTE_TYPE, $cellType ],
+                [ CellValueFormatter::XML_ATTRIBUTE_STYLE_ID, 123 ],
+            ]));
+
+        $nodeMock
+            ->expects($this->atLeastOnce())
+            ->method('getElementsByTagName')
+            ->with(CellValueFormatter::XML_NODE_VALUE)
+            ->will($this->returnValue($nodeListMock));
+
+        $styleHelperMock = $this->getMockBuilder(__NAMESPACE__ . '\StyleHelper')->disableOriginalConstructor()->getMock();
+
+        $styleHelperMock
+            ->expects($this->once())
+            ->method('shouldFormatNumericValueAsDate')
+            ->with(123)
+            ->will($this->returnValue(true));
+
+        $instance = new CellValueFormatter(null, $styleHelperMock);
+
+        $result = $instance->extractAndFormatNodeValue($nodeMock);
+
+        if ($expectedDateAsString === null) {
+            $this->assertNull($result);
+        } else {
+            $this->assertInstanceOf('DateTime', $result);
+            $this->assertSame($expectedDateAsString, $result->format('Y-m-d H:i:s'));
+        }
+    }
+
+}